Simplify: cos(pi/2+x)sin(-x)
cos(pi/2+x) = - sin x
(draw it on a graph , angle x to the left of y axis in quadrant 2)
also sin - x = - sin x
so we end up with
(-sin x)(-sin x) = sin^2 x
(draw it on a graph , angle x to the left of y axis in quadrant 2)
also sin - x = - sin x
so we end up with
(-sin x)(-sin x) = sin^2 x