Cosine of Full Angle

Theorem

 * $\cos 360 \degrees = \cos 2 \pi = 1$

where $\cos$ denotes cosine and $360 \degrees = 2 \pi$ is the full angle.

Proof
A direct implementation of Cosine of Multiple of Pi:
 * $\forall n \in \Z: \cos n \pi = \paren {-1}^n$

In this case, $n = 2$ and so:
 * $\cos 2 \pi = \paren {-1}^2 = 1$