Re: Simplifying algebraic expr: howto?
- To: mathgroup@smc.vnet.net
- Subject: [mg11397] Re: Simplifying algebraic expr: howto?
- From: "Daniel G. Hyams" <dgh2@Ra.MsState.EDU>
- Date: Sun, 8 Mar 1998 20:13:20 -0500
- Organization: Mississippi State University
- References: <6dqqf0$rk0@smc.vnet.net>
On 7 Mar 1998, Daniel G. Hyams wrote:
>
> I apologize for the (probable) simpleness of this questions, but I am
> new to mathamatica...
>
> I have an expression (for example):
>
> u*(nx*u + ny*v) ---- (1)
>
> and a definition:
>
> theta = nx*u+ny*v
>
> How do I get mathematica to simplify the expression (1) such that it
> returns:
>
> u*theta ?
Thanks to the couple of folks who responded to the questions, but I am
afraid that I did not make it clear enough...
The code that follows does indeed work:
T = (nx*u+ny*v)*u
T /. (nx*u+ny*v -> t)
Mathematica: t*u
But, this seems to do just a textual-type substitution. The following
snippet does not work (like I want it to):
T = (nx*u+ny*v)*u + (-nx*u-ny*v)*v
T /. (nx*u+ny*v -> t)
Mathematica: t*u + v(-nx*u - ny*v)
Obviously, the solution that I want is: t*u-t*v
The point is that the variable "t" is in a very complicated expression,
which can be considerably simplified by factoring it out, if only I
could tell Mathematica its identity. It also appears as
v*nx*u + ny*v^2 = v(nx*u + ny*v) = v*t
or
nx^2*u + 2*nx*ny*u*v + ny^2*v = (nx*u+ny*v)^2 = t^2
and I would like Mathematica to identify occurances like these.
----------------------------------------------------------- Daniel G.
Hyams
email: dhyams@ebicom.net
phone: (601) 323-4198
-----------------------------------------------------------
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