Re: Integration...

*To*: mathgroup at smc.vnet.net*Subject*: [mg24169] Re: [mg24133] Integration...*From*: Carl Woll <carlw at u.washington.edu>*Date*: Wed, 28 Jun 2000 22:50:50 -0400 (EDT)*References*: <200006280611.CAA13354@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Matthew, Rather than using NIntegrate, it's much simpler to use NDSolve to get f[t]. For example, if df[t] is the function you represented by f'[t], and a is 0, b is 1, and f[0]=0, then NDSolve[{f'[t]==df[t],f[0]==0},f,{t,0,1}] will return an interpolating function object which is precisely f[t]. Of course, as is evident above, in order to use NDSolve, you will need to supply initial conditions, which could be f[a] and g[a]. However, given only f'[t] and g'[t], there is no way to find out what f[a] and g[a] are. So, your problem is underspecified as given. Carl Woll "Yeung, Matthew" wrote: > Dear Sir, > > I am a Mathematica user and am having problems with one particular task that > I have to perform. > > I have 2 function, {f'(t),g'(t)}, that are unintegrable. I wish to plot the > parametric curve {f(t),g(t)} for a<t<b, say, but do not wish to use > NIntegrate as it will give me the result {f(T)-f(a),g(T)-g(a)}. > > Is there a way that I can find {f(a),g(a)} so that I can use NIntegrate; or > is it possible to evaluate the integral at one point? > > Thanks for your heklp and I look forward to hearing from you soon. > > Regards, > > Matt Yeung

**References**:**Integration...***From:*"Yeung, Matthew" <m.yeung@ic.ac.uk>