Re: symbolic approximation (formular manipulation)
- To: mathgroup at smc.vnet.net
- Subject: [mg55044] Re: symbolic approximation (formular manipulation)
- From: David Bailey <dave at Remove_Thisdbailey.co.uk>
- Date: Thu, 10 Mar 2005 05:25:04 -0500 (EST)
- References: <d0mnef$71b$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Zhe Hu wrote: > 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. > One answer is to replace R1->R2*eps1 and do a series expansion in eps1 and drop the higher terms. Then do the same with r2->R3*eps2 - because you have used symbolic small quantities, you can still recover your original variables. David Bailey dbaileyconsultancy.co.uk