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ZeroAT
Calculus - > Integral -> Substitution The question is sin 3x cos 3x dx Solve it by integrating using substitution.
Do you know what the derivate of \[\Large \sin(3x) \] is?
HINT: Let u be sin(3x).
How do you choose what to let u be? In this case you choose sin(3x) but why?
Takes some practice, but in case you consider taking u=cos(3x), that would also work. It's mainly about developing the idea of substitution. If you choose u=sin(3x) then: \[\Large \frac{du}{dx}=3\cos(3x) \]