Statement I: `f : A->B` is one - one and `g : B->C` is a one - one function, then `gof :A->C` is one - one Statement II : If `f:A->B, g:B->A` are two functions such that `gof=IA and fog=IB`, then `f=g-1.` Statement III : `f(x)=sec 2x-tan2x,g(x)=cosec2x-cot2x,` then `f=g`