Question

How do you verify `cos (pi/2 -x) cos x = cos x`?

Answer 1

See below

Explanation:

LHS =left hand side, RHS =right hand side

Use formula `cos(A-B)=cos A cos B + sin A sin B`

`=[cos (pi/2) cosx+sin (pi/2)sinx ]cosx`

`=[0 xx cosx +1 xx sinx]cosx`

`=sinx cosx`

Not cos x