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Thread Subject:
calculate coefficient values

Subject: calculate coefficient values

From: youngjin

Date: 9 Apr, 2010 02:49:19

Message: 1 of 3

Hello,

I have a problem on simplifying a symbolic equation. For example, if
we have the following equations which I made in another prgram,

==========================
syms M0 M1 M2 M3 M4 cphi sphi;

....

Eq(i,1) =
M0(i)^2-123686878722176832812117262693/4951760157141521099596496896*M1(i)^2*cphi(i)^2;
Eq(i,2) =
M0(i)^2-177223073697076064889572515693649/5070602400912917605986812821504*M2(i)^2*cphi(i)^2;
Eq(i,3) =
M0(i)^2-29648270679684750284166886836565/1267650600228229401496703205376*M3(i)^2*cphi(i)^2;

....

Eq(i,9) = M0(i)^3-M1(i)*M2(i)*M3(i)*M4(i);
========================

how can we simplify the value like
123686878722176832812117262693/4951760157141521099596496896 ?
Anybody has an idea?

Thanks.

Subject: calculate coefficient values

From: Roger Stafford

Date: 9 Apr, 2010 03:31:20

Message: 2 of 3

youngjin <hapticsys@gmail.com> wrote in message <336e4d09-a050-472d-93f1-7cddd9243e62@g11g2000yqe.googlegroups.com>...
> .........
> how can we simplify the value like
> 123686878722176832812117262693/4951760157141521099596496896 ?
> .........

  I'm afraid I have unhappy news for you. There is *no* way of simplifying the values you ask about without going to an approximation. Coming from a simplification of symbolic equations, they will already have been reduced as far as is possible if they are to remain exact. Of course you can always enter them into the non-symbolic part of matlab to get its best approximation with 'double' values using 'vpa', but you must realize these are only approximations.

Roger Stafford

Subject: calculate coefficient values

From: youngjin

Date: 9 Apr, 2010 15:55:49

Message: 3 of 3

Oh.....
Thanks for answer.

On Apr 8, 11:31 pm, "Roger Stafford"
<ellieandrogerxy...@mindspring.com.invalid> wrote:
> youngjin <haptic...@gmail.com> wrote in message <336e4d09-a050-472d-93f1-7cddd9243...@g11g2000yqe.googlegroups.com>...
> > .........
> > how can we simplify the value like
> > 123686878722176832812117262693/4951760157141521099596496896 ?
> > .........
>
>   I'm afraid I have unhappy news for you.  There is *no* way of simplifying the values you ask about without going to an approximation.  Coming from a simplification of symbolic equations, they will already have been reduced as far as is possible if they are to remain exact.  Of course you can always enter them into the non-symbolic part of matlab to get its best approximation with 'double' values using 'vpa', but you must realize these are only approximations.
>
> Roger Stafford

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