3 cos (x)
d / 3 \ --\cos (x)/ dx
Let u=cos(x)u = \cos{\left(x \right)}u=cos(x).
Apply the power rule: u3u^{3}u3 goes to 3u23 u^{2}3u2
Then, apply the chain rule. Multiply by ddxcos(x)\frac{d}{d x} \cos{\left(x \right)}dxdcos(x):
The derivative of cosine is negative sine:
The result of the chain rule is:
The answer is:
2 -3*cos (x)*sin(x)
/ 2 2 \ 3*\- cos (x) + 2*sin (x)/*cos(x)
/ 2 2 \ 3*\- 2*sin (x) + 7*cos (x)/*sin(x)