$$ \int \frac {1-\cos x}{(1+\cos x)\sin x} dx$$
I tried to expand the fraction by sin x and substitute t = cos x, so I got $$ \int \frac{(1-t)}{(1+t)(1-t)(1+t)} dt$$ here i could cancel out (1-t)... but what next? I don't know which formula should be used.