Re: "teach" mathematica an integral
- To: mathgroup at smc.vnet.net
- Subject: [mg54316] Re: "teach" mathematica an integral
- From: "julia" <dbug at hotmail.de>
- Date: Thu, 17 Feb 2005 10:30:38 -0500 (EST)
- Organization: Fraunhofer Gesellschaft (http://www.fraunhofer.de/)
- References: <curp29$qvk$1@smc.vnet.net> <cv08ns$j7e$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi, The term of a model, i need to transform is (0.25*a^2*Erf[(a - 2*b*x)/(2*(c*x)^0.5)])/(b^2*x^3) (a,b,c are parameters) The transformation, which mathematica didn't do was LaplaceTransform[Erf[(a - 2*b*x)/(2*Sqrt[c*x])], x, s] I performed the transformation by partial integration. This leads to ((-b)*E^((a*(b - a*Sqrt[c/a^2]*Sqrt[b^2/c + s]))/c) + (Sqrt[c] - a*Sqrt[c/a^2]*E^((a*(b - a*Sqrt[c/a^2]*Sqrt[b^2/c + s]))/c))* Sqrt[b^2/c + s])/(Sqrt[c]*s*Sqrt[b^2/c + s]) now i want to transform the first term. The Problem is that the Erf-Expression is part of a product... "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de> schrieb im Newsbeitrag news:cv08ns$j7e$1 at smc.vnet.net... > Hi, > > define: > > g /: Integrate[g[x_], x_] := q[x] > > and > > Integrate[g[z], z] > > gives > > q[z] > > since you hav not given the correct form fo the function you wish > > to integrate, I can only advice to use the most general form of te > integration, i.e., > > instead of the definition above > > Unprotect[Integrate] > Integrate[a_.*g[x_] + c_., x_] /; FreeQ[a, x] := a q[x] + c > Protect[Integrate] > > Regards > > Jens > > > > "julia" <dbug at hotmail.de> schrieb im Newsbeitrag > news:curp29$qvk$1 at smc.vnet.net... > > Hi group, > > > > I've had an integral (a laplace-transformation) which mathematica doesn't > > know. > > Now i have an analytic expression for the integral. > > Is there a possibility to add the new integral to mathematica (for example > > in any kind of library)? > > My problem is, that this integral is only a part of a longer formula for > > which i need the transformation... > > > > Thanks! > > > > > >