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Re: quadratic multiplication

  • To: mathgroup at smc.vnet.net
  • Subject: [mg84333] Re: quadratic multiplication
  • From: dh <dh at metrohm.ch>
  • Date: Wed, 19 Dec 2007 04:18:06 -0500 (EST)
  • References: <fk2v35$n96$1@smc.vnet.net> <fk5akt$5jc$1@smc.vnet.net> <fk74bj$6pt$1@smc.vnet.net>


Hi,

you need to give the variables in the statement:

mem[y_]:=MemberQ[{u1,u2,u3,u4,u5,u6},y];

If you introduce other variables, you must change the list {u1,...} to 

whatever your variables will be.

Hope this helps, Daniel



KFUPM wrote:

> On Dec 17, 11:05 am, dh <d... at metrohm.ch> wrote:

>> Hi,

>>

>> we may create a rule that sets all products of u^s to zero:

>>

>> mem[y_]:=MemberQ[{u1,u2,u3,u4,u5,u6},y];

>>

>> rules={y1_ y2_/;mem[y1]&&mem[y2]->0,y_^_/;mem[y]->0};

>>

>> here is an example:

>>

>> c1 u1+c2 u2+ c15 u1 u5 + c146 u1 u4 u6 /. rules

>>

>> hope this helps, Daniel

>>

>>

>>

>> KFUPM wrote:

>>> Dear all

>>> I have a very large expression which involves the multiplication of

>>> these variables:

>>> var ={u1,u2,u3,u4,u5,u6} with some other constants. In the expression,

>>> i want to suppress any quadratic or higher order multiplication of

>>> these varibles , e.g u1*u5  or u1*u4*u6 should be zero. And since, my

>>> expression is huge, i want to do this automatically. Any help in this

>>> regard is highly appreciated.

>>> Sincererly yours,

>>> HMQ- Hide quoted text -

>> - Show quoted text -

> 

> Thanks for your reply.

> 

> The rule didn't work for this term:

> 

> Out[103]=

> \!\(\*

>   RowBox[{\(5\/2\), " ", \(b\^4\), " ", \(x[2]\^4\), " ",

>     RowBox[{

>       SuperscriptBox["u11",

>         TagBox[\((1, 0, 0)\),

>           Derivative],

>         MultilineFunction->None], "[", \(x[1], x[3], t\), "]"}], " ",

>     RowBox[{

>       SuperscriptBox["u13",

>         TagBox[\((1, 0, 0)\),

>           Derivative],

>         MultilineFunction->None], "[", \(x[1], x[3], t\), "]"}]}]\)

> 

> Please note that b is a constant. So the varibles are only u11 u13.

> 

> I appreciate your help in this regard.

> 

> Thanks in anticipation.

> 

> 




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