F(x)=6 cos^5(3-1/12x^4) Найти f'(x)

Решите задачу:

$F(x)=6cos^5(3- \frac{1}{12}x^4 ) \\ \\ F'(x)=6*5cos^4(3- \frac{1}{12}x^4 )*(-sin(3- \frac{1}{12}x^4 ))*(- \frac{1}{12}*4x^3 )= \\ \\ =10x^3cos^4(3- \frac{1}{12}x^4 )sin(3- \frac{1}{12}x^4 )= \\ \\ =5x^3cos^3(3- \frac{1}{12}x^4 )*2cos(3- \frac{1}{12}x^4 )sin(3- \frac{1}{12}x^4 )= \\ \\ =5x^3cos^3(3- \frac{1}{12}x^4 )sin(2*(3- \frac{1}{12} x^4))= \\ \\ =5x^3cos^3(3- \frac{1}{12}x^4 )sin(6- \frac{1}{6} x^4)$