Cosine of Angle plus Three Right Angles

Theorem

 * $\cos \left({x + \dfrac {3 \pi} 2}\right) = \sin x$

Also see

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