integral 0 to infinite (x^ 3)(e^-8x) cos(5x) dx

should I do integrate by part?

help me (Worried)

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- Oct 22nd 2010, 08:17 PMddcampIntegration by parts? help plz
integral 0 to infinite (x^ 3)(e^-8x) cos(5x) dx

should I do integrate by part?

help me (Worried) - Oct 22nd 2010, 08:49 PMEducated
Please use brackets.

Is it: $\displaystyle \displaystyle \int_{0}^{\infty} x^3 \cdot e^{-8x} \cdot \cos (5x) dx$

Or is it: $\displaystyle \displaystyle \int_{0}^{\infty} x^{3e^{-8x}} \cdot \cos (5x) dx$ - Oct 22nd 2010, 10:47 PMddcamp
1st one. ! thanks. how did you do it?

- Oct 23rd 2010, 12:00 AMEducated
To type equations like I did, you use LaTeX to do it. LaTeX Tutorial.

Yes, you would use integration by parts. For the $\displaystyle \cos (5x)$ part you would also need to use integration by u-substitution as well as integration by parts.

$\displaystyle \displaystyle \int f'(x)g(x)h(x)dx = f(x)g(x)h(x) - \int f(x)g'(x)h(x)dx - \int f(x)g(x)h'(x)dx$ - Oct 23rd 2010, 04:25 AMskeeter
- Oct 23rd 2010, 11:41 AMddcamp
I have to find the actual value :S :S thanks!