Найти производную y= (cosx)/(sin^2 x) * ln tg x

[latex]y= \frac{cosx}{sin^2x}\cdot ln\, tgx\\\\y'= \frac{-sinx\cdot sin^2x-cosx\cdot 2sinx\cdot cosx}{sin^4x} \cdot ln\, tgx+ \frac{cosx}{sin^2x} \cdot \frac{1}{tgx}\cdot \frac{1}{cos^2x}=\\\\= \frac{-sin^2x-2cos^2x}{sin^3x} \cdot ln\, tgx+ \frac{1}{sin^3x} = \frac{1-ln\, tgx(sin^2x+2cos^2x)}{sin^3x} [/latex]