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Re: integrate problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg98854] Re: integrate problem
  • From: dh <dh at metrohm.com>
  • Date: Mon, 20 Apr 2009 19:08:21 -0400 (EDT)
  • References: <gshft4$c0o$1@smc.vnet.net>


Hi Sean,

consider:

  Integrate[1/(s[t] + a), t]

here the integration variable is t and s[t] is a unknown function. 

Therefore the argument, that contains an unknown function s[t], can not 

be integrated.

In

Integrate[1/(s[t] + a), s[t]]

the integration variable simply has a funny name of "s[t]"

Daniel



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.

> 

> Sean

> 




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