Answer
$ sin(\frac{\pi}{2}+x)=cosx$
Work Step by Step
Need to prove $ sin(\frac{\pi}{2}+x)=cosx$
$sin(A+B)=sinA cos B+cos A sin B$
Thus,
$ sin(\frac{\pi}{2}+x)=sin\frac{\pi}{2} cos x+cos \frac{\pi}{2} sin x$
$sin(\frac{\pi}{2}+x)=1*cos x+0*sin x$
Hence, $ sin(\frac{\pi}{2}+x)=cosx$
