338. Find the derivative of the function $y=\operatorname{tg} x^{5}$.
Solution. Here $u=x^{5}, y=\operatorname{tg} u$. Therefore,

$$
\left(\operatorname{tg} x^{5}\right)^{\prime}=\frac{1}{\cos ^{2} x^{5}} \cdot\left(x^{5}\right)^{\prime}=\frac{5 x^{4}}{\cos ^{2} x^{5}}
$$