Ребятки,помогите :) Найти производную
{(cos7x)`*sin6x-(sin6x)`*cos7x}/(sin6x)^2=-7sin7xsin6x-6cos6xcos7x}/sin^2 6x=
=-(6sin7xsin6x+6cos7xcos6x +sin7xsin6x)/sin^2 6x=(-6cos(7x-6x)+sin7xsin6x)/sin^ 6x=
={-6cosx+sin7xsin6x)/sin^6x