sin3x.cosx = 1 - sinx.cos3x; 2sin^2x - sin3x + sin5x = 0; sin3x + sinx = 2sin^2.2x

sin3x.cosx = 1 - sinx.cos3x
2sin^2x - sin3x + sin5x = 0
sin3x + sinx = 2sin^2.2x
giúp với ạ!