Re: integrate problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg98862] Re: integrate problem*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Mon, 20 Apr 2009 19:09:54 -0400 (EDT)

On 4/20/09 at 5:39 AM, 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 I asked you to integrate an arbitrary function of time and *did not* specify any details of the function could you do it? Note, this is exactly what you are asking Mathematica to do. >If the function that needs to be integrated w.r.t time is 1/(s[t] + >a), how do I accomplish that? define s[t] before asking Mathematica to do the integration >It seems like if integrate it wrt to s [t] it will work. >Integrate[1/(s[t] + a), s[t]] This is no different than Integrate[1/(s + a), s] If you want a solution in terms of t, you first have to define s[t]. There is no other way.