Cosine of Three Right Angles

Theorem

 * $\cos 270 \degrees = \cos \dfrac {3 \pi} 2 = 0$

where $\cos$ denotes cosine.

Also see

 * Sine of Three Right Angles
 * Tangent of Three Right Angles
 * Cotangent of Three Right Angles
 * Secant of Three Right Angles
 * Cosecant of Three Right Angles