i dont know how to use the forum's fraction option.

where did you got your sinX on the second side?

here is how you do it anyway,

cross multiply the first side(continued from the one that you are working) and you get sinX-sinXcosX/sinX

squared, then factor the numerator, you get sinX(1-cosX). cancel the sinX and the sinX from the denominator removing its

square. then you get (1-cosX)/sinX on the first side and sinX/1+cosX on the second. then from a/b=c/d equals a.d=c.b we get 1 - cosx

squared = sinX

squared.

thus we have proven the identity~