cos4x - cos2x = 2sinx
cos(3x+x)-cos(3x-x) = 2sinx
-2sin(3x)sinx - 2sinx = 0
sin(x)(sin3x+1) = 0
sinx = 0 или sin3x = -1
ответ:
cos4x - cos2x = 2sinx
cos(3x+x)-cos(3x-x) = 2sinx
-2sin(3x)sinx - 2sinx = 0
sin(x)(sin3x+1) = 0
sinx = 0 или sin3x = -1
ответ:![\displaystyle x=\{ \pi n; \frac{\pi }2+\frac{2\pi k}3\} ,\; n,k\in \mathbb{Z}](/tpl/images/1327/8375/4fc88.png)