Решите пример: cosx-cos3x=cos2x-cos4x
2sin2xsinx-2sin3xsinx=0 2sinx(sin2x-sin3x)=0 2sinx*2sin(x/2)cos(5x/2)=0 sinx=0⇒x=πn,n∈z sin(x/2)=0⇒x/2=πk,k∈z cos(5x/2)=0⇒5x/2=π/2+2πm,m∈z x=π/5+4ππm/5,m∈z