Question

докажите: sin x + sin 3x+ sin5x + sin7x= 4cos x cos 2 x sin 4x
СРОЧНО ​

Answer 1

sina*cosb=1/2(sin(a+b)+sin(a-b))
4cos x cos 2 x sin 4x= 2 cos2x(sin5x+sin3x)=2sin5xcos2x+2sin3xcos2x=
=sin7x+sin3x+sin5x+sinx
тождество доказано