Integration...

[T3achme_Isuck]

This is only my second post, so don't be too critical on me...lol.

This is actually a DiffEq. problem, but my problem is the Calculus, not the DE.
I need to integrate this, and I know it's the use of the integration by parts rule inside the integration by parts, but I keep missing it.

E^(-st)*cos(t)*t

(E raised to the -st multiplied by cos(t) and then by t).
I apologize for not knowing how to use symbols yet. Any help would be much appreciated.

 

[royhaas]

First get the answer to the integral of \(\displaystyle e^{-st}cos(t)\) and \(\displaystyle e^{-st}sin(t)\). You will need both these results. Then do the second integration by parts.

 

[T3achme_Isuck]

Yeah, I noticed you had an extra integration by parts, but from the point which I'm doing it, it seems to cance away. What am I doing wrong, if anything? Do you do parts inside of parts?

 

[royhaas]

You could also find \(\displaystyle F(s)=\int e^{-st}cos(t)dt\), then take the derivative \(\displaystyle F'(s)\).