y=cos−1(4x3−3x)+3sin−1x ........(1) Take cos−1(4x3−3x) Let us substitute x=cosθ in cos−1(4x3−3x) cos−1(4x3−3x)=cos−1(4cos3θ−3cosθ) =cos−1(cos3θ) =3θ =3cos−1x Now substitute the value of cos−1(4x3−3x) in equation (1) y=cos−1(4x3−3x)+3sin−1x =3cos−1x+3sin−1x As we know that, sin−1x+cos−1x=