三角関数の積分②

問題次の不定積分を求めよ。$${\small (1)}~\int\frac{\sin^2{x}}{1-\cos{x}}dx$$$${\small (2)}~\int\frac{2\cos^2{x}+3}{1-\sin^2{x}}dx$$$${\small (3)}~\int\tan^2{x}dx$$