317. Find $y^{\prime}$, if $y=\ln \sin ^{3} 5 x$.
Solution. We will use formulas VII, VIII, and XIII:

$$
y^{\prime}=\frac{1}{\sin ^{3} 5 x} \cdot 3 \sin ^{2} 5 x \cos 5 x \cdot 5=\frac{15 \cos 5 x}{\sin 5 x}=15 \operatorname{ctg} 5 x
$$

318-323. Find the derivatives of the following functions: