Question

Sin x - sin 2x + sin 3x - sin 4x = 0

Answer 1

$sin(x)-sin(2x)+sin(3x)-sin(4x)=0\\sin(x)-sun(4x)+sin(3x)-sin(2x)=0\\-2cos( \frac{5x}{2} )sin(\frac{3x}{2})+2cos(\frac{5x}{2})sin(\frac{x}{2})=0\\-2cos(\frac{5x}{2})(sin(\frac{3x}{2})-sin(\frac{x}{2}))=0\\cos(\frac{5x}{2})=0\\\frac{5x}{2}=\frac{\pi}{2}+\pi k\\x=\frac{\pi}{5}+\frac{2\pi k}{5}\\sin(\frac{3x}{2})-sin(\frac{x}{2})=0\\2cos( \frac{\frac{3x}{2}+\frac{x}{2}}{2} )sin(\frac{\frac{3x}{2}-\frac{x}{2}}{2})=2cos(\frac{2x}{2})sin(\frac{x}{2})=2cos(x)sin(\frac{x}{2})\\cos(x)=0\\x=\frac{\pi}{2}+\pik\\sin(\frac{x}{2})=0\\x=2\pik$
k∈Z
ответ:$x=\frac{\pi}{5}+\frac{2\pi k}{5}\\x=\frac{\pi k }{2}$