Re: symbolic approximation (formular manipulation)
- To: mathgroup at smc.vnet.net
- Subject: [mg55018] Re: symbolic approximation (formular manipulation)
- From: dh <dh at metrohm.ch>
- Date: Thu, 10 Mar 2005 05:24:18 -0500 (EST)
- References: <d0mnef$71b$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hello Zhe,
Try to formulate clearly what you want to do and the answer is obvious.
Because R1<<R2 you want to replace R1+R2 by R2
Because R2<<R3 you want to replace R2+R3 by R3
This can be done by ReplaceALL, abbreviated by /.
(R1+R2)/(R1(R2+R3)) /. {(R1+R2)->R2, R2+R3->R3}
have fun, Daniel
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.
>