## Task Condition

Find the derivative.

$y=\frac{\cos (\operatorname{ctg} 3) \cdot \cos ^{2} 14 x}{28 \sin 28 x}$
## Solution

$$
\begin{aligned}
& y^{\prime}=\left(\frac{\cos (\operatorname{ctg} 3) \cdot \cos ^{2} 14 x}{28 \sin 28 x}\right)^{\prime}=\frac{\cos (\operatorname{ctg} 3)}{28} \cdot\left(\frac{\cos ^{2} 14 x}{\sin 28 x}\right)^{\prime}= \\
& =\frac{\cos (\operatorname{ctg} 3)}{28} \cdot\left(\frac{\cos ^{2} 14 x}{2 \sin 14 x \cdot \cos 14 x}\right)^{\prime}=\frac{\cos (\operatorname{ctg} 3)}{56} \cdot(\operatorname{ctg} 14 x)^{\prime}= \\
& =\frac{\cos (\operatorname{ctg} 3)}{56} \cdot \frac{-1}{\sin ^{2} 14 x} \cdot 14=-\frac{\cos (\operatorname{ctg} 3)}{4 \sin ^{2} 14 x}
\end{aligned}
$$

## Problem Kuznetsov Differentiation 9-14