sin 4x + 2sin² 7x = 1

sin4x+2sin²7x-1=0sin4x-cos14x=0sin4x-sin(π/2-14x)=02sin(9x-π/4)cos(π/4-5x)=0sin(9x-π/4)=09x-π/4=πn9x=π/4+πnx=π/36+πn/9,n∈zcos(5x-π/4)=0 (косинус четная функция)5x-π/4=π/2+πk5x=3π/4+πkx=3π/20+πk/5,k∈z