Question

cos (pi/2 +x) cosx+ sin (pi/2+x)sinx=0

Answer 1

$\cos( \frac{\pi}{2} + x) \cos(x) + \sin(\frac{\pi}{2} + x) \sin(x) = 0 \\ \\ - \sin(x) \cos(x) + \cos(x) \sin(x) = 0 \\ \\ \cos(x) \sin(x) - \cos(x) \sin(x) = 0 \\ \\ 0 = 0$