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Re: integrate problem
*To*: mathgroup at smc.vnet.net
*Subject*: [mg98849] Re: integrate problem
*From*: Erik Max Francis <max at alcyone.com>
*Date*: Mon, 20 Apr 2009 19:07:27 -0400 (EDT)
*References*: <gshft4$c0o$1@smc.vnet.net>
sean_incali at yahoo.com wrote:
> I'm having some issues understanding this... Following works as
> expected.
>
> s is the variable in time. a is a parameter.
>
> Integrate[1/(s + a), s]
>
> gives Log[a + s]
>
> But the following gives the integral itself.
>
> Integrate[1/(s[t] + a), t]
>
> If the function that needs to be integrated w.r.t time is 1/(s[t] +
> a), how do I accomplish that? It seems like if integrate it wrt to s
> [t] it will work.
>
> Integrate[1/(s[t] + a), s[t]]
>
> But does that sound about right?
>
> Any thoughts appreciated.
In your examples, is a constant, but s[t] is a function of t. You
haven't specified what that function is, so Mathematica can't simplify
it beyond recognizing that you're asking for a symbolic integral.
Specify what s[t] is either inline in the Integrate function or
separately with a definition before trying to integrate 1/(s[t] + a).
--
Erik Max Francis && max at alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M, Skype erikmaxfrancis
Whom God has put asunder, why should man put together?
-- Ralph Waldo Emerson
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