Question

Решите пожалуйста математику

Answer 1

$\cos{21x}+\sin{21x}=0 \\ \\ \sin{21x}=-\cos{21x} \\ \\ tg \, 21x =-1 \\ \\ 21x=\frac{3\pi}{4}+\pi n, \ n\in Z \\ \\ x=\frac{3\pi}{84}+\frac{\pi n}{21}, \ n\in Z \\ \\ x=\frac{\pi}{28}+\frac{\pi n}{21}, \ n\in Z$

$\cos^2{x}-2\sin{x}\cdot \cos{x}=0 \\ \\ \cos{x}\cdot (\cos{x}-2\sin{x})=0 \\ \\ \cos{x}=0; \ \ \ \ \ \ \ \ \ \cos{x}=2\sin{x} \\ \\ x_1=\frac{\pi}{2}+\pin, \ n\in Z; \ \ \ 2tg \, x_2 =1 \\ \\ . \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ tg \, x_2 =\frac{1}{2} \\ \\ . \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x_2=arctg \, (\frac{1}{2})+\pi n, \ n\in Z$