LHS= cot x (1 - csc x)/ (1+csc x)(1 - csc x) (multiple both by (1 - csc x)
= cot x (1 -csc x ) / (1 - csc^2 x ) (diff of two sq)
= cot x ( 1 - csc x) / -cot^2 x ( formula 1 + cot^2 = csc^2 x), thus 1 - csc^2 = - cot^2 x)
= (csc x - 1)/ cot x (cancel the cot x and multiply -1)
= RHS