## Calculus: Early Transcendentals 8th Edition

$cos(\frac{\pi}{2}-x)=sinx$
Need to prove $cos(\frac{\pi}{2}-x)=sinx$ $cos(A-B)=cos A cos B+sinA sin B$ Thus, $cos(\frac{\pi}{2}-x)=cos \frac{\pi}{2} cos x+sin\frac{\pi}{2} sin x$ $cos(\frac{\pi}{2}-x)=0*cos x+1*sin x$ Hence, $cos(\frac{\pi}{2}-x)=sinx$