What is sin(x+pi/2)sin(x+π2)?

1 Answer
Apr 16, 2015

cos x

With pi/2π2 add to any angle measure, sin changes to cos and vice- versa. Hence It would change to cosine and since the angle measure falls in the second quadrant, hence sin(x+pi/2π2) would be positive.

Alternatively sin(x+pi/2π2)= sin x cos pi/2π2 + cos x sinpi/2π2. Since cos pi/2π2 is 0 and sinpi/2π2 is 1, it would be equal to cosx