Question

# ( int cos ^{-1}left(4 x^{3}-3 xright) d x )

Solution

( int cos ^{-1}left(4 x^{3}-3 xright) d x )

( Rightarrow operatorname{let} x=cos theta )

( Rightarrow operatorname{ses}^{-1}left(4 cos theta^{3}-3 cos thetaright) )

( Rightarrow int cos ^{-1}(cos 3 theta) )

( Rightarrow 3 theta )

( Rightarrow 3 cos ^{-1} x )