# Antiderivative of 2^t

• Apr 5th 2009, 05:53 PM
cammywhite
Antiderivative of 2^t
$\int 2^t dt$

I know the derivative of $2^t$ is $2^tln2$, but I can't figure out the anitderivative
• Apr 5th 2009, 05:54 PM
Mush
Quote:

Originally Posted by cammywhite
$\int 2^t dt$

I know the derivative of $2^t$ is $2^tln2$, but I can't figure out the anitderivative

$2^t = e^{\ln(2^t)} = e^{t\ln(2)}$

Hence

$I = \int e^{t\ln(2)}dt$

Can you handle that?
• Apr 5th 2009, 06:49 PM
cammywhite
Quote:

Originally Posted by Mush
$2^t = e^{\ln(2^t)} = e^{t\ln(2)}$

Hence

$I = \int e^{t\ln(2)}dt$

Can you handle that?

I got

$\frac {e^{t\ln(2)}} {ln2}$
• Apr 5th 2009, 06:50 PM
Jhevon
Quote:

Originally Posted by cammywhite
I got

$\frac {e^{t\ln(2)}} {ln2} ~{\color{red} + C}$

correct. but what is $e^{t \ln 2}$?
• Apr 5th 2009, 06:58 PM
cammywhite
Can I simplify the following function?
what do you mean?

Oh is it $2^x$
• Apr 5th 2009, 07:05 PM
Jhevon
Quote:

Originally Posted by cammywhite
what do you mean?

Oh is it $2^x$

where is $x$ coming from? it is $2^t$.

in general, $\int a^x~dx = \frac {a^x}{\ln a} + C$, for $a > 1$ a constant

and we derive this in the same way you did here, by considering $\int e^{x \ln a}~dx$
• Apr 5th 2009, 07:13 PM
cammywhite
Quote:

Originally Posted by Jhevon
where is $x$ coming from? it is $2^t$.

in general, $\int a^x~dx = \frac {a^x}{\ln a} + C$, for $a > 0$ a constant

and we derive this in the same way you did here, by considering $\int e^{x \ln a}~dx$

$
\int 2^t dt = \frac {2^t}{ln2}+C
$
• Apr 5th 2009, 07:18 PM
Jhevon
Quote:

Originally Posted by cammywhite
$
\int 2^t dt = \frac {2^t}{ln2}+C
$

• Apr 5th 2009, 07:31 PM
Krizalid
Quote:

Originally Posted by Jhevon

in general, $\int a^x~dx = \frac {a^x}{\ln a} + C$, for $a > 0$ a constant

We're so mentalized on stating that but in this case it's actually $a>1.$ :)
• Apr 5th 2009, 07:32 PM
Jhevon
Quote:

Originally Posted by Krizalid
We're so mentalized on stating that but in this case it's actually $a>1.$ :)

yes, of course. ">0" is so fun to say (Nod)
• Apr 5th 2009, 09:07 PM
Reckoner
Quote:

Originally Posted by Krizalid
We're so mentalized on stating that but in this case it's actually $a>1.$ :)

Of course, it is only necessary for $a>0$ and $a\neq1.$ That is, $a\in(0,1)\cup(1,\infty).$
• Apr 6th 2009, 08:00 PM
Jhevon
Quote:

Originally Posted by Reckoner
Of course, it is only necessary for $a>0$ and $a\neq1.$ That is, $a\in(0,1)\cup(1,\infty).$

why, you're right! i guess ">1" should be added to the list of things that are fun to say but not think about. right behind "let $\epsilon > 0$" :)