Re: Factorising
- To: mathgroup at smc.vnet.net
- Subject: [mg38948] Re: Factorising
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 22 Jan 2003 06:10:16 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <b0jfvt$t90$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
a) as long as Times[] has the Listable attribute it will
not work to get a expression like a*{x,y,z} because
Times will scatter a across the vector elements
b) what is with
m = {(a - 2*wone*Sin[a*t])/4, (a - 2*wone*Sin[a*t])/4, (a +
2*wone*Sin[a*t])/
4, (a + 2*wone*Sin[a*t])/4, (-a - 2*Sqrt[a^2 +
wone^2*Sin[a*t]^2])/
4, (-a - 2*Sqrt[a^2 + wone^2*Sin[a*t]^2])/
4, (-a + 2*Sqrt[a^2 + wone^2*Sin[a*t]^2])/
4, (-a + 2*Sqrt[a^2 + wone^2*Sin[a*t]^2])/4};
a*Hold[Evaluate[Apart[#/a] & /@ m]] /. a_*Hold[b_] :> Hold[a*b]
Regards
Jens
Chris Rodgers wrote:
>
> Hi
>
> How can I tell Mathematica to pull a particular factor out of an expression.
>
> For example in this expression:
> {(a - 2*wone*Sin[a*t])/4, (a - 2*wone*Sin[a*t])/4, (a + 2*wone*Sin[a*t])/4,
> (a + 2*wone*Sin[a*t])/4,
> (-a - 2*Sqrt[a^2 + wone^2*Sin[a*t]^2])/4, (-a - 2*Sqrt[a^2 +
> wone^2*Sin[a*t]^2])/4,
> (-a + 2*Sqrt[a^2 + wone^2*Sin[a*t]^2])/4, (-a + 2*Sqrt[a^2 +
> wone^2*Sin[a*t]^2])/4}
>
> I would like to bring the "a" out to the front of the expression, even
> outside the matrix.
>
> How can I ask Mathematica to do this, and how can I stop the "a" just
> floating back into the main expression?
>
> Yours
>
> Chris Rodgers
> St John's College
> http://rodgers.org.uk/