Question

csc^2-cosx secx=cot^2

Answer 1

first you have to use this
1+cot^2x=csc^2x

Answer 2

then observe what you can do next

Answer 3

Or, starting from the left side,
\[\cos x\sec x=\frac{\cos x}{\cos x}=1\]
so you have
\[\csc^2x-1=\cot^2x\]