Question

tan x-1/tan x+1=1-cot x/1+cotx

Answer 1

$\dfrac{\tan x-1}{\tan x+1}=\dfrac{\frac{\sin x}{\cos x}-1}{\frac{\sin x}{\cos x}+1}=\dfrac{\sin x-\cos x}{\sin x+\cos x}=\dfrac{1-\frac{\cos x}{\sin x}}{1+\frac{\cos x}{\sin x}}=\dfrac{1-\cot x}{1+\cot x}$