Question

Решить уравнение 2sinx*sin2x+cos3x=0

Answer 1

2sinx*2sinxcosx+4cos^3x-3cosx

Answer 2

$2sinx*sin2x+cos3x=0$
$2* \frac{1}{2}[cos(x-2x)-cos(x+2x)]+cos3x=0$
$cosx-cos3x+cos3x=0$
$cosx=0$
$x= \frac{ \pi }{2} + \pi n,$ $n$ ∈ $Z$

$sinx*siny= \frac{1}{2} [cos(x-y)-cos(x+y)]$