Sinasinb=1/2(cos(a-b)-cos(a+b))
1/2(cos2x-cos16x)=1/2(cos6x-cos16x)
cos2x-cos16x=cos6x-cos16x
cos2x-cos6x=0
cosa-cosb=-2sin(a-b)/2sin(a+b)/2
2sin2xsin4x=0
sin2x=0⇒2x=πn⇒x=πn/2
sin4x=0⇒4x=πn⇒x=πn/4-общее
-π<πn/4<3π/4<br>-4n=-3⇒x=-3π/4
n=-2⇒x=-2π/4
n=-1⇒x=-π/4
n=0⇒x=0
n=1⇒x=π/4
n=2⇒x=2π/4
-3π/4-2π/4-π/4+0+π/4+2π/4=-3π/4