sin(pi/2+x)cos(pi-x)cot(3pi/+x)=sin(pi/2-x)sin(3pi/2-x)cot(pi/2+x

Answer 1

use your sum/formulas. For example,

sin(pi/2+x) = cosx
cos(pi-x) = -cosx

and so on. Then the products will be much easier to manipulate.