Condition of the problem

Find the derivative.

$$
y=\cos (\ln 13)-\frac{1}{44} \cdot \frac{\cos ^{2} 22 x}{\sin 44 x}
$$
## Solution

$y^{\prime}=\left(\cos (\ln 13)-\frac{1}{44} \cdot \frac{\cos ^{2} 22 x}{\sin 44 x}\right)^{\prime}=0-\frac{1}{44} \cdot\left(\frac{\cos ^{2} 22 x}{\sin 44 x}\right)^{\prime}=$

$=-\frac{1}{44} \cdot\left(\frac{\cos ^{2} 22 x}{2 \sin 22 x \cdot \cos 22 x}\right)^{\prime}=-\frac{1}{88} \cdot\left(\frac{\cos 22 x}{\sin 22 x}\right)^{\prime}=$

$=-\frac{1}{88} \cdot(\operatorname{ctg} 22 x)^{\prime}=-\frac{1}{88} \cdot \frac{-1}{\sin ^{2} 22 x} \cdot 22=\frac{1}{4 \sin ^{2} 22 x}$

Problem Kuznetsov Differentiation 9-22