Question

write (tanx-1/tanx+1) in terms of cot x

Answer 1

\[\cot(x)=\frac{ 1 }{ \tan(x) }\]
Therefore,
\[\tan(x)=\frac{ 1 }{ \cot(x) }\]

Substitute that for every tan(x) you see and you have your expression in terms of x, albeit a bit uglier.

Answer 2

Thank you very much :-)