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SkyEye
Registered User regular

Ugh. I don't even remember if this was in Calc I or II.

Anyway, I'm integrating exp(-Dt)dt. If I set u=exp(-D), v=exp(t), I get exp(-Dt). If I set u=1, x=exp(-Dt), I get -1/D*exp(-Dt). Those are not the same. Why aren't they the same?

Oh, good luck, ceres!

Anyway, I'm integrating exp(-Dt)dt. If I set u=exp(-D), v=exp(t), I get exp(-Dt). If I set u=1, x=exp(-Dt), I get -1/D*exp(-Dt). Those are not the same. Why aren't they the same?

Oh, good luck, ceres!

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## Posts

ceresonalso, this might help

Usagionprettysure the correct answer is the second one but I can't figure out why the first one doesn't work.SkyEyeonwhy are you integrating by parts?

Usagionu = exp(-D)

v = exp(t)

Then

uv = exp(-D) * exp(t) = exp(-D + t) =/= exp(-Dt)

?

ecco the dolphinonThe product of exp(-D) and exp(t) is exp(-D + t).

EDIT: Oops, eeccccoo beat me to it. Guess I should actually read the other replies before making my own :P

ClipseonSkyEyeonNah, don't fuss.

You're not the first person to have made this mistake.

Besides, now that you've made the mistake publicly, you'll remember when it comes to your exam!

ecco the dolphinon