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I had this show up in a problem and I went completely blank. How do I compute

$\int a^t \mathrm{d}t$

where $a$ is some constant?

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    @RickDecker Everything's easy when you know how. I didn't have access to a table of integrals at the time and, even if I did, I wanted to learn how to work it out. What a ridiculous reason to downvote.2013-05-23

5 Answers 5

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$a^t = e^{t \ln a}$.

From there, $\int a^t dt = \int e^{t \ln a} dt$, which is trivial to integrate. The answer is $\frac{a^t}{\ln a} + k$

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Note that $a^t = (e^{\log(a)})^t = e^{t \log (a)}$ and $\int e^{bt} dt = \dfrac{e^{bt}}{b} + \text{ constant}$

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$\int a^tdt=1/\log(a) \cdot \int a^t \log(a)dt=a^t/ \log(a)+C$ This is because the derivative of $a^t$ is $a^t \log(a)$ .

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    Try `\log($a$)` instead of `log(a)`.2012-11-17
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Since $\dfrac{\text{d}}{\text{dt}} a^t=a^t\ln(a),$ we have $\int a^t \text{dt}=\dfrac{a^t}{\ln(a)}+C$

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Use the fact that $\frac{\text{d}(a^t)}{\text{d}t}=a^t\ln(a)$