Verify the identity. cos quanity x plus pi divided by two = -sin x

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

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step-by-step explanation: