cos^2 3x=sin^2 4x умножим на 2 2cos^2 3x=2sin^2 4x 1+cos6x=1-cos8x cos8x+cos6x=0 2cos7xcosx=0 cos7x=0 cosx=0 x=П/14+Пn/7, n-целое x=Пn, n-целое