Ctga - 1/1-tga + ctga-1 срочно надо

Решите задачу:

$\frac{\overbrace {ctgx-1}}{1-tgx}+\underbrace {ctgx-1}=(ctgx-1)\cdot ( \frac{1}{1-tgx} +1)= \\\\=(\frac{cosx}{sinx}-1)\cdot (\frac{1}{1-\frac{sinx}{cosx}}+1)= \frac{cosx-sinx}{sinx}\cdot ( \frac{cosx}{cosx-sinx}+1)=\\\\= \frac{cosx}{sinx} + \frac{cosx-sinx}{sinx} = \frac{2cosx-sinx}{sinx} = \frac{2cosx}{sinx} -\frac{sinx}{sinx} =2ctgx-1\\\\ili$

$\frac{ctgx-1}{1-tgx} +ctgx-1=\frac{\frac{cosx}{sinx}-1}{1-\frac{sinx}{cosx}} +ctgx-1=\frac{(cosx-sinx)cosx}{(cosx-sinx)sinx}+ctgx-1=\\\\= \frac{cosx}{sinx}+ctgx-1=ctgx+ctgx-1=2ctgx-1$