`int sin3x cos 4x dx`

Explanation

`intsin3x cos 4x dx=(1)/(2) int 2 cos 4x sin 3x dx`
`=(1)/(2)int(sin 7x-sinx)dx`
`=(1)/(2)(-(cos7x)/(7)+cosx)+c`
`=-(1)/(14)cos 7x+(1)/(2)cosx+c`