Re: symbolic approximation (formular manipulation)
- To: mathgroup at smc.vnet.net
- Subject: [mg55050] Re: [mg54991] symbolic approximation (formular manipulation)
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 10 Mar 2005 05:25:17 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
I haven't tested this much but it should give you a start. approx[expr_, x_<y_] := Module[{k}, (Factor[expr/.x->k*y]/.(k+z_)->z)/. k->x/y]; expr=(R1+R2)/(R1(R2+R3)); approx[expr,R1<R2] R2/(R1*(R2 + R3)) approx[%,R2<R3] R2/(R1*R3) Bob Hanlon > > From: Zhe Hu <iamhuzhe at gmail.com> To: mathgroup at smc.vnet.net > Date: 2005/03/09 Wed AM 06:34:18 EST > To: mathgroup at smc.vnet.net > Subject: [mg55050] [mg54991] symbolic approximation (formular manipulation) > > A formula in electrical engineering can be simplified after assuming, > e.g. R1<<R2, within 10% error tolerance. > > How this kind of "simplify" or approximation can be performed by Mathematica? > > For example, R1<<R2, R2<<R3 > > R1+R2 R2 R2 > --------------- ---> ------------------ ---------> ------------------ > R1(R2+R3) R1(R2+R3) R1 R3 > > > > I thought about replacing: R1->0.00001*R2, but that would eliminate R1 > completely from the formula (denumerator), which is not favorable in > some cases. > >