sin 2 theta=2 cot theta - (2cos^2 theta)/tan theta
RHS:2 cot theta - (2cos^2 theta)/tan theta=2/tan theta - 2cos^2 theta/ tan theta
=(2(1-cos^2 theta))/tan theta
=(2sin^2 theta)/tan theta
=(2 sin^2 theta) / (sin theta/ cos theta)
=2 sin^2 theta * cos theta/ sin theta
=2 sin theta cos theta
=sin 2 theta
=LHS