Пожалуйста срочно! Помогите решить! ctgx cos^2*ydx+sin^2 *xtgydy=0 (ответ tg^2y=ctg^2*x+2C

Решите задачу:

$\cot(x) \cos^2(y) dx + \sin^2(x) \tan(y) dy = 0\\\frac{\sin(y)}{\cos^3(y)} \, dy = -\frac{\cos(x)}{\sin^3(x)} dx\\\int \frac{\sin(y)}{\cos^3(y)} \, dy = -\int \frac{\cos(x)}{\sin^3(x)} dx\\\int \tan(y) \, d\tan(y) = \int \cot(x) \, d\cot (x)\\\frac12 \tan^2(y) = \frac 12(\cot^2(x) + c_1)\\y = \arctan\left(\pm \sqrt{\cot^2(x) + c_1}\right)$