Найти производную y = sin^2 (3x +1) +7

Y =sin² (3x+1) +7 ;

y '=(sin² (3x+1) +7) '=(sin² (3x+1)) ' +(7) ' =2sin(3x+1)*(sin(3x+1))' +0 =
2sin(3x+1)*cos(3x+1)*(3x+1)'  = sin2*(3x+1)*((3x)' +(1))' =sin(6x+2)*(3(x)' +0) =
3sin(6x+2) .