Cosine of Angle plus Right Angle

Theorem

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

Also see

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