Question

${ \cot }^{2} \alpha - \frac{1}{ { \sin }^{2} \alpha } = - 1 \\ \\ prove \: it \: \: \: ...$

Answer 1

I am taking a instead of alpha

cot2 a-1/sin2a=cot2 a-cosec2 a=-(cosec2 a-cot2a) =-(1)=-1
hope it helps you