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...
attributio
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095d85d4ef
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ede934369b
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3b41ea714a
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3
authors.toml
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3
authors.toml
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@ -0,0 +1,3 @@
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[authors."mark"]
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email = "mark@betalupi.com"
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webpage = "betalupi.com"
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@ -62,8 +62,7 @@ Let's expand $#sym.RR$ to include a tropical additive identity.
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#problem()
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Do tropical additive inverses exist? \
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#note([
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Is there an inverse $y$ for every $x$ so that $x #tp y = #sym.infinity$? \
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Remember that $#sym.infinity$ is the additive identity.
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Is there an inverse $y$ for every $x$ so that $x #tp y = #sym.infinity$?
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])
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#solution([
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@ -278,7 +277,7 @@ Fill the following tropical addition and multiplication tables
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#problem()
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Expand and simplify $f(x) = (x #tp 2)(x #tp 3)$, then evaluate $f(1)$ and $f(4)$ \
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#hint([Adjacent parenthesis imply tropical multiplication])
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Adjacent parenthesis imply tropical multiplication
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#solution([
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$
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@ -20,7 +20,7 @@ for some nonnegative integer $n$ and coefficients $c_0, c_1, ..., c_n$. \
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The _degree_ of a polynomial is the largest $n$ for which $c_n$ is nonzero.
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#theorem()
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The _fundamental theorem of algebra_ states that any non-constant polynomial with real coefficients
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The _fundamental theorem of algebra_ implies that any non-constant polynomial with real coefficients
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can be written as a product of polynomials of degree 1 or 2 with real coefficients.
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#v(2mm)
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@ -30,8 +30,8 @@ can be written as $(x^2 + 2x+5)(x-2)(x+4)(x+4)$
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#v(2mm)
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A similar theorem exists for polynomials with complex coefficients. \
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These coefficients may be found using the _roots_ of this polynomial. \
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As you already know, there are formulas that determine the roots of quadratic, cubic, and quartic #note([(degree 2, 3, and 4)]) polynomials. There are no formulas for the roots of polynomials with larger degrees---in this case, we usually rely on appropriate roots found by computers.
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These coefficients may be found using the roots of this polynomial. \
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As it turns out, there are formulas that determine the roots of quadratic, cubic, and quartic #note([(degree 2, 3, and 4)]) polynomials. There are no formulas for the roots of polynomials with larger degrees---in this case, we usually rely on approximate roots found by computers.
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#v(2mm)
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In this section, we will analyze tropical polynomials:
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@ -100,7 +100,7 @@ In other words, find $r$ and $s$ so that
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),
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)
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#note([Naturally, we will call $r$ and $s$ the _roots_ of $f$.])
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we will call $r$ and $s$ the _roots_ of $f$.
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#solution([
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Because $(x #tp r)(x #tp s) = x^2 #tp (r #tp s)x #tp s r$, we must have $r #tp s = 1$ and $r #tm s = 4$. \
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@ -116,8 +116,7 @@ In other words, find $r$ and $s$ so that
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#v(1fr)
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#problem()
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Can you see the roots of this polynomial in the graph? \
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#hint([Yes, you can. What "features" do the roots correspond to?])
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How can we use the graph to determine these roots?
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#solution([The roots are the corners of the graph.])
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@ -317,7 +316,7 @@ into linear factors.
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#v(2mm)
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Whenever we say "the roots of $f$", we really mean "the roots of $accent(f, macron)$." \
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Also, $f$ and $accent(f, macron)$ might be the same polynomial.
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$f$ and $accent(f, macron)$ might be the same polynomial.
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#problem()
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If $f(x) = a x^2 #tp b x #tp c$, then $accent(f, macron)(x) = a x^2 #tp B x #tp c$ for some $B$. \
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|
35
src/Warm-Ups/A Familiar Concept/main.tex
Executable file
35
src/Warm-Ups/A Familiar Concept/main.tex
Executable file
@ -0,0 +1,35 @@
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\documentclass[
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solutions,
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hidewarning,
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singlenumbering,
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nopagenumber
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]{../../../lib/tex/ormc_handout}
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\usepackage{../../../lib/tex/macros}
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\title{Warm-Up: A Familiar Concept}
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\uptitler{\smallurl{}}
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\subtitle{Prepared by Mark on \today}
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\begin{document}
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\maketitle
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\problem{}<one>
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Let $v = [-5, -2, 0, 1, 4, 1000]$. Find all $x$ that minimize the following metric. \par
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$$
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\sum_{\forall i} |v_i - x| = |v_1 - x| + |v_2 - x| + ... + |v_6 - x|
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$$
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\vfill
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\problem{}
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Let $v = [-5, -2, 0, 1, 4, 1000, 1001]$. Find all $x$ that minimize the metric in \ref{one}.
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\vfill
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\problem{}
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What is this metric usually called?
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\end{document}
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@ -1,39 +0,0 @@
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#import "@local/handout:0.1.0": *
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#show: doc => handout(
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doc,
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quarter: link(
|
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"https://betalupi.com/handouts",
|
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"betalupi.com/handouts",
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),
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title: [Warm-Up: A Familiar Concept],
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by: "Mark",
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)
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#problem()
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Let $v = [-5, -2, 0, 1, 4, 1000]$. Find all $x$ that minimize the following metric:
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#align(
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center,
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box(
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inset: 3mm,
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$
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sum_(#sym.forall i) |v_i - x| = |v_1 - x| + |v_2 - x| + ... + |v_6 - x|
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$,
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),
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)
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#v(1fr)
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#problem()
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Let $v = [-5, -2, 0, 1, 4, 1000, 1001]$. Find all $x$ that minimize the metric in the previous problem.
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#v(1fr)
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#problem()
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What is this metric usually called?
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#v(0.25fr)
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31
src/Warm-Ups/Fuse Timers/main.tex
Executable file
31
src/Warm-Ups/Fuse Timers/main.tex
Executable file
@ -0,0 +1,31 @@
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\documentclass[
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||||
solutions,
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||||
hidewarning,
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||||
singlenumbering,
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||||
nopagenumber
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]{../../../lib/tex/ormc_handout}
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\usepackage{../../../lib/tex/macros}
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\title{Warm-Up: Fuse Timers}
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\uptitler{\smallurl{}}
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\subtitle{Prepared by Mark on \today.}
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\begin{document}
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\maketitle
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\problem{}
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Suppose we have two strings and a lighter. Each string takes an hour to fully burn. \par
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However, we do not know how fast each part of the string burns:
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half might burn in 1 minute, and the rest could take 59.
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\vspace{2mm}
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How would we measure exactly 45 minutes using these strings?
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\vfill
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\end{document}
|
@ -1,21 +0,0 @@
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#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
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||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Warm-Up: Fuse Timers],
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by: "Mark",
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)
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#problem()
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Suppose we have two strings and a lighter. Each string takes exactly an hour to fully burn. \
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However, we do not know how fast each part of the string burns:
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half might burn in 1 minute, and the rest could take 59.
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#v(2mm)
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How can we measure exactly 45 minutes using these two strings?
|
54
src/Warm-Ups/Mario Kart/main.tex
Executable file
54
src/Warm-Ups/Mario Kart/main.tex
Executable file
@ -0,0 +1,54 @@
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\documentclass[
|
||||
solutions,
|
||||
hidewarning,
|
||||
singlenumbering,
|
||||
nopagenumber
|
||||
]{../../../lib/tex/ormc_handout}
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||||
\usepackage{../../../lib/tex/macros}
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||||
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\title{Warm-Up: Mario Kart}
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\uptitler{\smallurl{}}
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\subtitle{Prepared by Mark on \today}
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\begin{document}
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\maketitle
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\problem{}
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A standard Mario Kart cup consists of 12 players and four races. \par
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Each race is scored as follows:
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\begin{itemize}
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\item 15 points are awarded for first place;
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\item 12 for second;
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\item and $(13 - \text{place})$ otherwise.
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\end{itemize}
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In any one race, no players may tie.
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A player's score at the end of a cup is the sum of their scores for each of the four races.
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\vspace{2mm}
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An $n$-way tie occurs when the top $n$ players have the same score at the end of a round. \par
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What is the largest possible $n$, and how is it achieved?
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\begin{solution}
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A 12-way tie is impossible, since the total number of point is not divisible by 12.
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\vspace{2mm}
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A 11-way tie is possible, with a top score of 28:
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\begin{itemize}
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\item Four players finish $1^\text{st}$, $3^\text{ed}$, $11^\text{th}$, and $12^\text{th}$;
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% spell:off
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\item Four players finish $2^\text{nd}$, $4^\text{th}$, $9^\text{th}$, and $10^\text{th}$;
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% spell:on
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\item Two players finish fifth twice and seventh twice,
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\item One player finishes sixth in each race.
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\end{itemize}
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The final player always finishes eighth, with a non-tie score of 20.
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\end{solution}
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||||
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\end{document}
|
@ -1,41 +0,0 @@
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||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Warm-Up: Mario Kart],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
#problem()
|
||||
A standard Mario Kart cup consists of 12 players and four races. \
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||||
Each race is scored as follows:
|
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- 15 points are awarded for first place;
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||||
- 12 for second;
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||||
- and $(13 - #text("place"))$ otherwise.
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||||
|
||||
In any one race, no players may tie. \
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||||
A player's score at the end of a cup is the sum of their scores for each of the four races.
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||||
|
||||
#v(2mm)
|
||||
|
||||
An $n$-way tie occurs when the top $n$ players have the same score at the end of a round. \
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||||
What is the largest possible $n$, and how is it achieved?
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||||
|
||||
#solution([
|
||||
A 12-way tie is impossible, since the total number of point is not divisible by 12.
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||||
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||||
#v(2mm)
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||||
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||||
A 11-way tie is possible, with a top score of 28:
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- Four players finish $1^#text("st")$, $3^#text("ed")$, $11^#text("th")$, and $12^#text("th")$;
|
||||
- Four players finish $2^#text("nd")$, $4^#text("th")$, $9^#text("th")$, and $10^#text("th")$;
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- Two players finish fifth twice and seventh twice,
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||||
- One player finishes sixth in each race.
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||||
The final player always finishes eighth, with a non-tie score of 20.
|
||||
|
||||
])
|
@ -4,3 +4,8 @@ title = "Odd Dice"
|
||||
[publish]
|
||||
handout = true
|
||||
solutions = true
|
||||
|
||||
[[attribution]]
|
||||
who = "mark"
|
||||
when = 2024-02-13
|
||||
what = "Initial version of handout"
|
||||
|
57
src/Warm-Ups/Partition Products/main.tex
Executable file
57
src/Warm-Ups/Partition Products/main.tex
Executable file
@ -0,0 +1,57 @@
|
||||
\documentclass[
|
||||
solutions,
|
||||
singlenumbering,
|
||||
nopagenumber
|
||||
]{../../../lib/tex/ormc_handout}
|
||||
\usepackage{../../../lib/tex/macros}
|
||||
|
||||
|
||||
\title{Warm-Up: Partition Products}
|
||||
\uptitler{\smallurl{}}
|
||||
\subtitle{Prepared by Mark on \today.}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\maketitle
|
||||
|
||||
\problem{}
|
||||
Take any positive integer $n$. \par
|
||||
Now, write it as sum of smaller positive integers: $n = a_1 + a_2 + ... + a_k$ \par
|
||||
Maximize the product $a_1 \times a_2 \times ... \times a_k$
|
||||
|
||||
|
||||
|
||||
\begin{solution}
|
||||
|
||||
\textbf{Interesting Solution:}
|
||||
|
||||
Of course, all $a_i$ should be greater than $1$. \par
|
||||
Also, all $a_i$ should be smaller than four, since $x \leq x(x-2)$ if $x \geq 4$. \par
|
||||
Thus, we're left with sequences that only contain 2 and 3. \par
|
||||
\note{Note that two twos are the same as one four, but we exclude fours for simplicity.}
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
Finally, we see that $3^2 > 2^3$, so any three twos are better repackaged as two threes. \par
|
||||
The best sequence $a_i$ thus consists of a maximal number of threes followed by 0, 1, or 2 twos.
|
||||
|
||||
\linehack{}
|
||||
|
||||
|
||||
|
||||
\textbf{Calculus Solution:}
|
||||
|
||||
First, solve this problem for equal, non-integer $a_i$:
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
We know $n = \prod{a_i}$, thus $\ln(n) = \sum{\ln(a_i)}$. \par
|
||||
If all $a_i$ are equal, we get $\ln(n) = k \times \ln(n / k)$. \par
|
||||
Derive wrt $k$ and set to zero to get $\ln(n / k) = 1$ \par
|
||||
So $k = n / e$ and $n / k = e \approx 2.7$
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
If we try to approximate this with integers, we get the same solution as above.
|
||||
\end{solution}
|
||||
\end{document}
|
@ -1,47 +0,0 @@
|
||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Warm-Up: Partition Products],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
#problem()
|
||||
Take any positive integer $n$. \
|
||||
Now, write it as sum of smaller positive integers: $n = a_1 + a_2 + ... a_k$ \
|
||||
Maximize the product $a_1 #sym.times a_2 #sym.times ... #sym.times a_k$
|
||||
|
||||
|
||||
#solution([
|
||||
*Interesting Solution:*
|
||||
|
||||
Of course, all $a_i$ should be greater than $1$. \
|
||||
Also, all $a_i$ should be smaller than four, since $x <= x(x-2)$ if $x >= 4$. \
|
||||
Thus, we're left with sequences that only contain 2 and 3. \
|
||||
#note([Note that two twos are the same as one four, but we exclude fours for simplicity.])
|
||||
|
||||
#v(2mm)
|
||||
|
||||
Finally, we see that $3^2 > 2^3$, so any three twos are better repackaged as two threes. \
|
||||
The best sequence $a_i$ thus consists of a maximal number of threes followed by 0, 1, or 2 twos.
|
||||
|
||||
#v(8mm)
|
||||
|
||||
*Calculus Solution:*
|
||||
|
||||
First, solve this problem for equal, real $a_i$:
|
||||
#v(2mm)
|
||||
We know $n = product(a_i)$, thus $ln(n) = sum(ln(a_i))$. \
|
||||
If all $a_i$ are equal, we get $ln(n) = k #sym.times ln(n / k)$. \
|
||||
Derive wrt $k$ and set to zero to get $ln(n / k) = 1$ \
|
||||
So $k = n / e$ and $n / k = e #sym.approx 2.7$
|
||||
|
||||
#v(2mm)
|
||||
|
||||
If we try to approximate this with integers, we get the same solution as above.
|
||||
])
|
34
src/Warm-Ups/Prime Factors/main.tex
Executable file
34
src/Warm-Ups/Prime Factors/main.tex
Executable file
@ -0,0 +1,34 @@
|
||||
\documentclass[
|
||||
solutions,
|
||||
singlenumbering,
|
||||
nopagenumber,
|
||||
hidewarning
|
||||
]{../../../lib/tex/ormc_handout}
|
||||
\usepackage{../../../lib/tex/macros}
|
||||
|
||||
\title{Warm-Up: Prime Factors}
|
||||
\uptitler{\smallurl{}}
|
||||
\subtitle{Prepared by Mark on \today.}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\maketitle
|
||||
|
||||
\problem{}
|
||||
What proportion of integers have $2$ as their smallest prime factor?
|
||||
% 1^2
|
||||
\vfill
|
||||
|
||||
|
||||
\problem{}
|
||||
What proportion of integers have $3$ as their second-smallest prime factor?
|
||||
% 1/6
|
||||
\vfill
|
||||
|
||||
|
||||
\problem{}
|
||||
What is the median second-smallest prime factor?
|
||||
% 37
|
||||
\vfill
|
||||
|
||||
\end{document}
|
@ -1,29 +0,0 @@
|
||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Warm-Up: Prime Factors],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
#problem()
|
||||
What proportion of integers have $2$ as their smallest prime factor?
|
||||
#solution([$1 div 2$])
|
||||
#v(1fr)
|
||||
|
||||
|
||||
#problem()
|
||||
What proportion of integers have $3$ as their second-smallest prime factor?
|
||||
#solution([$1 div 6$])
|
||||
#v(1fr)
|
||||
|
||||
|
||||
#problem()
|
||||
What is the median second-smallest prime factor?
|
||||
#solution([37])
|
||||
#v(1fr)
|
153
src/Warm-Ups/Regex/main.tex
Normal file
153
src/Warm-Ups/Regex/main.tex
Normal file
@ -0,0 +1,153 @@
|
||||
\documentclass[
|
||||
solutions,
|
||||
hidewarning,
|
||||
]{../../../lib/tex/ormc_handout}
|
||||
\usepackage{../../../lib/tex/macros}
|
||||
|
||||
|
||||
\usepackage{xcolor}
|
||||
\usepackage{soul}
|
||||
\usepackage{hyperref}
|
||||
|
||||
\definecolor{Light}{gray}{.90}
|
||||
\sethlcolor{Light}
|
||||
\newcommand{\htexttt}[1]{\texttt{\hl{#1}}}
|
||||
|
||||
|
||||
\title{The Regex Warm-Up}
|
||||
\uptitler{\smallurl{}}
|
||||
\subtitle{Prepared by Mark on \today}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\maketitle
|
||||
|
||||
|
||||
Last time, we discussed Deterministic Finite Automata. One interesting application of these mathematical objects is found in computer science: Regular Expressions. \par
|
||||
This is often abbreviated \say{regex}, which is pronounced like \say{gif.}
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
Regex is a language used to specify patterns in a string. You can think of it as a concise way to define a DFA, using text instead of a huge graph. \par
|
||||
|
||||
Often enough, a clever regex pattern can do the work of a few hundred lines of code.
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
Like the DFAs we've studied, a regex pattern \textit{accepts} or \textit{rejects} a string. However, we don't usually use this terminology with regex, and instead say that a string \textit{matches} or \textit{doesn't match} a pattern.
|
||||
|
||||
\vspace{5mm}
|
||||
|
||||
Regex strings consist of characters, quantifiers, sets, and groups.
|
||||
|
||||
\vspace{5mm}
|
||||
|
||||
\textbf{Quantifiers} \par
|
||||
Quantifiers specify how many of a character to match. \par
|
||||
There are four of these: \htexttt{+}, \htexttt{*}, \htexttt{?}, and \htexttt{\{ \}}
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
\htexttt{+} means \say{match one or more of the preceding token} \par
|
||||
\htexttt{*} means \say{match zero or more of the preceding token}
|
||||
|
||||
For example, the pattern \htexttt{ca+t} will match the following strings:
|
||||
\begin{itemize}
|
||||
\item \texttt{cat}
|
||||
\item \texttt{caat}
|
||||
\item \texttt{caaaaaaaat}
|
||||
\end{itemize}
|
||||
\htexttt{ca+t} will \textbf{not} match the string \texttt{ct}. \par
|
||||
The pattern \htexttt{ca*t} will match all the strings above, including \texttt{ct}.
|
||||
\vspace{2mm}
|
||||
|
||||
|
||||
\htexttt{?} means \say{match one or none of the preceding token} \par
|
||||
The pattern \htexttt{linea?r} will match only \texttt{linear} and \texttt{liner}.
|
||||
\vspace{2mm}
|
||||
|
||||
Brackets \htexttt{\{min, max\}} are the most flexible quantifier. \par
|
||||
They specify exactly how many tokens to match: \par
|
||||
\htexttt{ab\{2\}a} will match only \texttt{abba}. \par
|
||||
\htexttt{ab\{1,3\}a} will match only \texttt{aba}, \texttt{abba}, and \texttt{abbba}. \par
|
||||
% spell:off
|
||||
\htexttt{ab\{2,\}a} will match any \texttt{ab...ba} with at least two \texttt{b}s.
|
||||
% spell:on
|
||||
|
||||
\vspace{5mm}
|
||||
|
||||
\problem{}
|
||||
Write the patterns \htexttt{a*} and \htexttt{a+} using only \htexttt{\{ \}}.
|
||||
\vfill
|
||||
|
||||
\problem{}
|
||||
Draw a DFA equivalent to the regex pattern \htexttt{01*0}.
|
||||
\vfill
|
||||
|
||||
\pagebreak
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
\textbf{Characters, Sets, and Groups} \par
|
||||
In the previous section, we saw how we can specify characters literally: \par
|
||||
\texttt{a+} means \say{one or more \texttt{a} character}
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
There are, of course, other ways we can specify characters.
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
The first such way is the \textit{set}, denoted \htexttt{[ ]}. A set can pretend to be any character inside it. \par
|
||||
For example, \htexttt{m[aoy]th} will match \texttt{math}, \texttt{moth}, or \texttt{myth}. \par
|
||||
\htexttt{a[01]+b} will match \texttt{a0b}, \texttt{a111b}, \texttt{a1100110b}, and any other similar string. \par
|
||||
You may negate a set with a \htexttt{\textasciicircum}. \par
|
||||
\htexttt{[\textasciicircum abc]} will match any character except \texttt{a}, \texttt{b}, or \texttt{c}, including symbols and spaces.
|
||||
|
||||
\vspace{2mm}
|
||||
|
||||
If we want to keep characters together, we can use the \textit{group}, denoted \htexttt{( )}. \par
|
||||
|
||||
Groups work exactly as you'd expect, representing an atomic\footnotemark{} group of characters. \par
|
||||
\htexttt{a(01)+b} will match \texttt{a01b} and \texttt{a010101b}, but will \textbf{not} match \texttt{a0b}, \texttt{a1b}, or \texttt{a1100110b}.
|
||||
|
||||
\footnotetext{In other words, \say{unbreakable}}
|
||||
|
||||
|
||||
\problem{}<regex>
|
||||
You are now familiar with most of the tools regex has to offer. \par
|
||||
Write patterns that match the following strings:
|
||||
\begin{enumerate}[itemsep=1mm]
|
||||
\item An ISO-8601 date, like \texttt{2022-10-29}. \par
|
||||
\hint{Invalid dates like \texttt{2022-13-29} should also be matched.}
|
||||
|
||||
\item An email address. \par
|
||||
\hint{Don't forget about subdomains, like \texttt{math.ucla.edu}.}
|
||||
|
||||
\item A UCLA room number, like \texttt{MS 5118} or \texttt{Kinsey 1220B}.
|
||||
|
||||
\item Any ISBN-10 of the form \texttt{0-316-00395-7}. \par
|
||||
\hint{Remember that the check digit may be an \texttt{X}. Dashes are optional.}
|
||||
|
||||
\item A word of even length. \par
|
||||
\hint{The set \texttt{[A-z]} contains every english letter, capitalized and lowercase. \\
|
||||
\texttt{[a-z]} will only match lowercase letters.}
|
||||
|
||||
\item A word with exactly 3 vowels. \par
|
||||
\hint{The special token \texttt{\textbackslash w} will match any word character. It is equivalent to \texttt{[A-z0-9\_]} \\ \texttt{\_} stands for a literal underscore.}
|
||||
|
||||
\item A word that has even length and exactly 3 vowels.
|
||||
|
||||
\item A sentence that does not start with a capital letter.
|
||||
\end{enumerate}
|
||||
|
||||
\vfill
|
||||
|
||||
\problem{}
|
||||
If you'd like to know more, check out \url{https://regexr.com}. It offers an interactive regex prompt, as well as a cheatsheet that explains every other regex token there is. \par
|
||||
You will find a nice set of challenges at \url{https://alf.nu/RegexGolf}.
|
||||
I especially encourage you to look into this if you are interested in computer science.
|
||||
\end{document}
|
@ -1,138 +0,0 @@
|
||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [The Regex Warm-Up],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
|
||||
Last time, we discussed Deterministic Finite Automata. One interesting application of these mathematical objects is found in computer science: Regular Expressions. \
|
||||
This is often abbreviated "regex," which is pronounced like "gif."
|
||||
|
||||
#v(2mm)
|
||||
|
||||
Regex is a language used to specify patterns in a string. You can think of it as a concise way to define a DFA, using text instead of a huge graph. \
|
||||
|
||||
Often enough, a clever regex pattern can do the work of a few hundred lines of code.
|
||||
|
||||
#v(2mm)
|
||||
|
||||
Like the DFAs we've studied, a regex pattern _accepts_ or _rejects_ a string. However, we don't usually use this terminology with regex, and instead say that a string _matches_ or _doesn't match_ a pattern.
|
||||
|
||||
#v(5mm)
|
||||
|
||||
Regex strings consist of characters, quantifiers, sets, and groups.
|
||||
|
||||
#v(5mm)
|
||||
|
||||
|
||||
|
||||
*Quantifiers* \
|
||||
Quantifiers specify how many of a character to match. \
|
||||
There are four of these: `+`, `*`, `?`, and `{ }`.
|
||||
|
||||
#v(4mm)
|
||||
|
||||
`+` means "match one or more of the preceding token" \
|
||||
`*` means "match zero or more of the preceding token"
|
||||
|
||||
For example, the pattern `ca+t` will match the following strings:
|
||||
- `cat`
|
||||
- `caat`
|
||||
- `caaaaaaaat`
|
||||
`ca+t` will *not* match the string `ct`. \
|
||||
The pattern `ca*t` will match all the strings above, including `ct`.
|
||||
|
||||
|
||||
#v(4mm)
|
||||
|
||||
|
||||
`?` means "match one or none of the preceding token" \
|
||||
The pattern `linea?r` will match only `linear` and `liner`.
|
||||
|
||||
#v(4mm)
|
||||
|
||||
Brackets `{min, max}` are the most flexible quantifier. \
|
||||
They specify exactly how many tokens to match: \
|
||||
`ab{2}a` will match only `abba`. \
|
||||
`ab{1,3}a` will match only `aba`, `abba`, and `abbba`. \
|
||||
`ab{2,}a` will match any `ab...ba` with at least two `b`s.
|
||||
|
||||
#problem()
|
||||
Write the patterns `a*` and `a+` using only `{ }`.
|
||||
#v(1fr)
|
||||
|
||||
#problem()
|
||||
Draw a DFA equivalent to the regex pattern `01*0`.
|
||||
#v(1fr)
|
||||
|
||||
#pagebreak()
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
*Characters, Sets, and Groups* \
|
||||
In the previous section, we saw how we can specify characters literally: \
|
||||
`a+` means "one or more `a` characters" \
|
||||
There are, of course, other ways we can specify characters.
|
||||
|
||||
#v(4mm)
|
||||
|
||||
The first such way is the _set_, denoted `[ ]`. A set can pretend to be any character inside it. \
|
||||
For example, `m[aoy]th` will match `math`, `moth`, or `myth`. \
|
||||
`a[01]+b` will match `a0b`, `a111b`, `a1100110b`, and any other similar string. \
|
||||
|
||||
#v(4mm)
|
||||
|
||||
We can negate a set with a `^`. \
|
||||
`[^abc]` will match any single character except `a`, `b`, or `c`, including symbols and spaces.
|
||||
|
||||
#v(4mm)
|
||||
|
||||
If we want to keep characters together, we can use the _group_, denoted `( )`. \
|
||||
|
||||
Groups work exactly as you'd expect, representing an atomic#footnote([In other words, "unbreakable"]) group of characters. \
|
||||
`a(01)+b` will match `a01b` and `a010101b`, but will *not* match `a0b`, `a1b`, or `a1100110b`.
|
||||
|
||||
#problem()
|
||||
You are now familiar with most of the tools regex has to offer. \
|
||||
Write patterns that match the following strings:
|
||||
|
||||
- An ISO-8601 date, like `2022-10-29`. \
|
||||
#hint([Invalid dates like `2022-13-29` should also be matched.])
|
||||
|
||||
- An email address. \
|
||||
#hint([Don't forget about subdomains, like `math.ucla.edu`.])
|
||||
|
||||
- A UCLA room number, like `MS 5118` or `Kinsey 1220B`.
|
||||
|
||||
- Any ISBN-10 of the form `0-316-00395-7`. \
|
||||
#hint([Remember that the check digit may be an `X`. Dashes are optional.])
|
||||
|
||||
- A word of even length. \
|
||||
#hint([The set `[A-z]` contains every english letter, capitalized and lowercase. \
|
||||
`[a-z]` will only match lowercase letters.])
|
||||
|
||||
- A word with exactly 3 vowels. \
|
||||
#hint([The special token `\w` will match any word character. \
|
||||
It is equivalent to `[A-z0-9_]`. `_` represents a literal underscore.
|
||||
])
|
||||
|
||||
- A word that has even length and exactly 3 vowels.
|
||||
|
||||
- A sentence that does not start with a capital letter.
|
||||
#v(1fr)
|
||||
|
||||
#problem()
|
||||
If you'd like to know more, check out `https://regexr.com`.
|
||||
It offers an interactive regex prompt,
|
||||
as well as a cheatsheet that explains every other regex token there is. \
|
||||
You can find a nice set of challenges at `https://alf.nu/RegexGolf`.
|
30
src/Warm-Ups/Travellers/main.tex
Executable file
30
src/Warm-Ups/Travellers/main.tex
Executable file
@ -0,0 +1,30 @@
|
||||
\documentclass[
|
||||
solutions,
|
||||
singlenumbering,
|
||||
nopagenumber
|
||||
]{../../../lib/tex/ormc_handout}
|
||||
\usepackage{../../../lib/tex/macros}
|
||||
|
||||
\title{Warm-Up: Travellers}
|
||||
\uptitler{\smallurl{}}
|
||||
\subtitle{Prepared by Mark on \today}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\maketitle
|
||||
|
||||
\problem{}
|
||||
Four travellers are on a plane, each moving along a straight line at an arbitrary constant speed. \par
|
||||
No two of their paths are parallel, and no three intersect at the same point. \par
|
||||
We know that traveller A has met travelers B, C, and D, \par
|
||||
and that traveller B has met C and D (and A). Show that C and D must also have met. \par
|
||||
|
||||
\begin{solution}
|
||||
When a body travels at a constant speed, its graph with respect to time is a straight line. \par
|
||||
So, we add time axis in the third dimension, perpendicular to our plane. \par
|
||||
Naturally, the projection of each of these onto the plane corresponds to a road.
|
||||
|
||||
Now, note that two intersecting lines define a plane and use the conditions in the problem to show that no two lines are parallel.
|
||||
\end{solution}
|
||||
|
||||
\end{document}
|
@ -1,26 +0,0 @@
|
||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Warm-Up: Travellers],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
#problem()
|
||||
Four travellers are on a plane, each moving along a straight line at an arbitrary constant speed. \
|
||||
No two of their paths are parallel, and no three intersect at the same point. \
|
||||
We know that traveller A has met travelers B, C, and D, \
|
||||
and that traveller B has met C and D (and A). Show that C and D must also have met.
|
||||
|
||||
#solution([
|
||||
When a body travels at a constant speed, its graph with respect to time is a straight line. \
|
||||
So, we add time axis in the third dimension, perpendicular to our plane. \
|
||||
Naturally, the projection of each of these onto the plane corresponds to a road.
|
||||
|
||||
Now, note that two intersecting lines define a plane and use the conditions in the problem to show that no two lines are parallel.
|
||||
])
|
22
src/Warm-Ups/fmod/main.tex
Executable file
22
src/Warm-Ups/fmod/main.tex
Executable file
@ -0,0 +1,22 @@
|
||||
\documentclass[
|
||||
solutions,
|
||||
hidewarning,
|
||||
singlenumbering,
|
||||
nopagenumber
|
||||
]{../../../lib/tex/ormc_handout}
|
||||
\usepackage{../../../lib/tex/macros}
|
||||
|
||||
|
||||
\title{Warm-Up: \texttt{fmod}}
|
||||
\uptitler{\smallurl{}}
|
||||
\subtitle{Prepared by Mark on \today.}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\maketitle
|
||||
|
||||
\problem{}
|
||||
I'm sure you're all familiar with how \texttt{mod(a, b)} and \texttt{remainder(a, b)} work with integers. \par
|
||||
Devise an equivalent for floats (i.e, real numbers).
|
||||
|
||||
\end{document}
|
@ -1,16 +0,0 @@
|
||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Warm-Up: `fmod`],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
#problem()
|
||||
I'm sure you're all familiar with how `mod(a, b)` and `remainder(a, b)` \ work when `a` and `b` are integers.
|
||||
Devise an equivalent for floats (i.e, real numbers).
|
Reference in New Issue
Block a user