what is the diffential solution of cot3x dy/dx-3y=cos3x+sin3x

equation can be rewritten as dy/dx - 3tan3x y = sin3x + sin3x tan3x

implies integrating factor is exp(D^-1(-3tan3x)) = exp(-ln sec3x) = cos3x

which implies y cos3x = D^-1(sin3x cos3x + sin²3x) = 1/12(-cos3x) + x/2 - 1/12(sin3x)

implies y = 1/2(x sec3x) -1/12(1+ tan3x)