Answer:
see below
Step-by-step explanation:
cos ( x+pi/2) = -sinx
We know that
cos(A + B) = cos A cos B - sin A sin B
Let x = A and pi/2 = B
cos x cos pi/2 - sin x sin pi/2 = -sin x
We know cos pi/2 = 0 and sin pi/2 = 1
cos x * 0 - sin x *1 = -sin x
- sin x = - sin x
