diff --git a/src/evaluate/function.rs b/src/evaluate/function.rs
index 73c9e61..ac95a3b 100644
--- a/src/evaluate/function.rs
+++ b/src/evaluate/function.rs
@@ -2,8 +2,30 @@ use crate::parser::Expression;
 use crate::parser::Function;
 use crate::parser::Operator;
 use crate::parser::LineLocation;
+use crate::quantity::FreeUnit;
+use crate::quantity::WholeUnit;
+use crate::quantity::Quantity;
+use crate::quantity::Scalar;
 use super::EvalError;
 
+
+// If unitless, do nothing
+// If compatible with radians, convert to radians and return unitless
+// Otherwise, error.
+//
+// Used for trig functions.
+fn to_radians(q: Quantity) -> Result<Quantity, ()> {
+	if q.unitless() { return Ok(q); }
+
+	let mut r = Quantity::new_rational(1f64).unwrap();
+	r.insert_unit(FreeUnit::from_whole(WholeUnit::Radian), Scalar::new_rational(1f64).unwrap());
+	let Some(q) = q.convert_to(r) else { return Err(()) };
+
+	return Ok(q.without_unit());
+}
+
+
+
 pub fn eval_function(g: &Expression) -> Result<Expression, (LineLocation, EvalError)> {
 
 	let Expression::Operator(loc, Operator::Function(f), args) = g else {panic!()};
@@ -16,6 +38,56 @@ pub fn eval_function(g: &Expression) -> Result<Expression, (LineLocation, EvalEr
 	match f {
 		Function::NoUnit => { return Ok(Expression::Quantity(*loc + *l, q.without_unit())); }
 		Function::ToBase => { return Ok(Expression::Quantity(*loc + *l, q.convert_to_base())); }
+
+		// Trigonometry
+		Function::Sin => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.sin()));
+		},
+		Function::Cos => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.cos()));
+		},
+		Function::Tan => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.tan()));
+		},
+		Function::Csc => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.csc()));
+		},
+		Function::Sec => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.sec()));
+		},
+		Function::Cot => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.cot()));
+		},
+		Function::Sinh => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.sinh()));
+		},
+		Function::Cosh => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.cosh()));
+		},
+		Function::Tanh => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.tanh()));
+		},
+		Function::Csch => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.csch()));
+		},
+		Function::Sech => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.sech()));
+		},
+		Function::Coth => {
+			let Ok(q) = to_radians(q.clone()) else { return Err((*loc + *l, EvalError::IncompatibleUnit)); };
+			return Ok(Expression::Quantity(*loc + *l, q.coth()));
+		},
 		_ => {}
 	}
 
@@ -32,30 +104,28 @@ pub fn eval_function(g: &Expression) -> Result<Expression, (LineLocation, EvalEr
 		Function::NaturalLog => { return Ok(Expression::Quantity(*loc + *l, q.ln())); },
 		Function::TenLog => { return Ok(Expression::Quantity(*loc + *l, q.log10())); },
 
-		Function::Sin => { return Ok(Expression::Quantity(*loc + *l, q.sin())); },
-		Function::Cos => { return Ok(Expression::Quantity(*loc + *l, q.cos())); },
-		Function::Tan => { return Ok(Expression::Quantity(*loc + *l, q.tan())); },
 		Function::Asin => { return Ok(Expression::Quantity(*loc + *l, q.asin())); },
 		Function::Acos => { return Ok(Expression::Quantity(*loc + *l, q.acos())); },
 		Function::Atan => { return Ok(Expression::Quantity(*loc + *l, q.atan())); },
 
-		Function::Csc => { return Ok(Expression::Quantity(*loc + *l, q.csc())); },
-		Function::Sec => { return Ok(Expression::Quantity(*loc + *l, q.sec())); },
-		Function::Cot => { return Ok(Expression::Quantity(*loc + *l, q.cot())); },
-
-		Function::Sinh => { return Ok(Expression::Quantity(*loc + *l, q.sinh())); },
-		Function::Cosh => { return Ok(Expression::Quantity(*loc + *l, q.cosh())); },
-		Function::Tanh => { return Ok(Expression::Quantity(*loc + *l, q.tanh())); },
 		Function::Asinh => { return Ok(Expression::Quantity(*loc + *l, q.asinh())); },
 		Function::Acosh => { return Ok(Expression::Quantity(*loc + *l, q.acosh())); },
 		Function::Atanh => { return Ok(Expression::Quantity(*loc + *l, q.atanh())); },
 
-		Function::Csch => { return Ok(Expression::Quantity(*loc + *l, q.csch())); },
-		Function::Sech => { return Ok(Expression::Quantity(*loc + *l, q.sech())); },
-		Function::Coth => { return Ok(Expression::Quantity(*loc + *l, q.coth())); },
-
 		Function::ToBase
 		| Function::NoUnit
+		| Function::Sin
+		| Function::Cos
+		| Function::Tan
+		| Function::Csc
+		| Function::Sec
+		| Function::Cot
+		| Function::Sinh
+		| Function::Cosh
+		| Function::Tanh
+		| Function::Csch
+		| Function::Sech
+		| Function::Coth
 		=> unreachable!()
 	}
 }
\ No newline at end of file
diff --git a/src/quantity/mod.rs b/src/quantity/mod.rs
index 93607ec..4c9dc90 100644
--- a/src/quantity/mod.rs
+++ b/src/quantity/mod.rs
@@ -16,12 +16,13 @@ cross-compilation to other systems. RUG does not work on all systems.
 */
 
 mod scalar;
-pub(in crate::quantity) use crate::quantity::scalar::Scalar;
+pub use crate::quantity::scalar::Scalar;
 
 
 mod unit;
 pub use crate::quantity::unit::Unit;
 pub use crate::quantity::unit::FreeUnit;
+pub use crate::quantity::unit::WholeUnit;
 
 mod quantity;
 pub use crate::quantity::quantity::Quantity;
diff --git a/src/tests.rs b/src/tests.rs
index b17c8be..df72d28 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -220,6 +220,11 @@ fn complex_units() {
 
 #[test]
 fn functions() {
+	good_expr("1", "sin(90 deg)");
+	good_expr("-1", "cos(180 deg)");
+	good_expr("0.70711", "sin(pi/4)");
+	good_expr("0.70711", "sin((pi/4) r)");
+
 	good_expr("2", "nounit(2 mm)");
 	good_expr("2", "nounit(2 meter * second)");
 	//good_expr("5000 m²·g/(s²·A²)", "tobase(5H)");