cos2x=cos^2x-sin^2x=1-2sin^2x заменяем в уравении 2(1-2sin^2x)-8sinx+3=0
4х+5=6+5 (х-3)
4х+5=6+5х-15
4х+5=5х-9
9+5=х
х=14
<span>cos8x * cos5x -((-sin5x)*sin8x)=cos8x * cos5x +sin5x*sin8х=cos(8х-5х)=cos(3х)</span>
(4х² - 2х + 3 ) + ( - 2х² + 3х ) =
= (4х² - 2х²) + ( - 2х + 3х) + 3 =
= 2х² + х + 3