This looks like a half angle fromula with 2x instead of x, so try a half angle identity.

Since you have the sign of a sum try the sum identity for sins#2

sin(x + pi/2)= cos x

replace tan and sec with their definitions in terms of sins and cosines and simplify#3

tan^2(x) = sec^2(x)= sin^2(x) - cos^2(x)

This is equivalent to:#4

cot(x)/(1 + csc(x)) = (csc(x) - 1)/ cot(x)

cot^2(x)=(csc(x)+1)(csc(x)-1)=csc^2(x)-1

Now replace everything with its definition in terms of sins and cosins and simplify both sides.

CB