Evaluate: (i) `intsin3xcos4x\ dx` (ii) `intcos2xcos4x\ dx`

Explanation

`I=\int \sin ^{3} x \cos 4 x d x`


`\text { let } \cos x=t \text {. }`


`\sin x d x=d t .`


`d x=\frac{-d t}{\sin x}`


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