Compare commits
2 Commits
1d8782a03b
...
ca8426284a
| Author | SHA1 | Date | |
|---|---|---|---|
| ca8426284a | |||
| 7d29d0e416 |
@@ -8,4 +8,17 @@
|
||||
|
||||
#problem()
|
||||
$n$ black and $n$ white points are randomly distributed on a plane. No three points are collinear.\
|
||||
Show that it is always possible draw $n$ nonintersecting lines between pairs of points of different colors.
|
||||
Show that it is always possible to draw $n$ nonintersecting lines between pairs of points of different colors.
|
||||
|
||||
#solution([
|
||||
Consider the total length of all lines on the plane.
|
||||
|
||||
#v(2mm)
|
||||
|
||||
If we replace a pair of intersecting lines with two nonintersecting lines, \
|
||||
we strictly decrease this total length (by the triangle inequality).
|
||||
|
||||
#v(2mm)
|
||||
Thus, the arrangement of lines with the minimum total length must not have any intersections. \
|
||||
Showing that a minimum exists is fairly easy.
|
||||
])
|
||||
|
||||
Reference in New Issue
Block a user