Question

sec^2(pi/2-x)-1=cot^2x where do i start

Answer 1

First, for trig functions, func(π/2-x) = cofunc(x). So,

sec^2(π/2-x) = csc^2(x)

now our equation looks like

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

QED
It would have helped if you had specified you were looking for a proof, rather than trying to solve an equation.