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Re: What's wrong with this assuming?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111121] Re: What's wrong with this assuming?
  • From: Sam Takoy <sam.takoy at yahoo.com>
  • Date: Wed, 21 Jul 2010 07:11:52 -0400 (EDT)
  • References: <i242rv$opo$1@smc.vnet.net>

Thanks for all this response and all that haven't showed up on the 
newsgroup yet.

Here's my actual problem:

Assuming[ a Cosh[H/(2 a)] == 1,
  FullSimplify[
   Cosh[H/a] +
    1/2 ((H/a - H/a Cosh[H/a] + 2 Sinh[H/a]) Sinh[H/(2 a)] )/(
     H/(2 a) Sinh[H/(2 a)] - 1/a)]]

and the answer is "1";

My version of Mathematica (7) fails to do this simplification.

Thanks again!





On 7/20/2010 7:55 AM, Bob Hanlon wrote:
> Use the assumption directly in Simplify or FullSimplify
>
> Simplify[(x^2 + x)^2 + h, x^2 + x == h]
>
> h (h+1)
>
> FullSimplify[(x^2 + x)^2 + h, x^2 + x == h]
>
> h (h+1)
>
> Or put Simplify or FullSimplify within the scope of the Assuming construct
>
> Assuming[x^2 + x == h, Simplify[(x^2 + x)^2 + h]]
>
> h (h+1)
>
> Assuming[x^2 + x == h, FullSimplify[(x^2 + x)^2 + h]]
>
> h (h+1)
>
>
> Bob Hanlon
>
> ---- Sam Takoy<sam.takoy at yahoo.com>  wrote:
>
> =============
> Hi,
>
>
> I have a situation where I have to simplify an expression that contains
> x and h, but x is given implicitly by h, so I can't explicitly eliminate
> it. So here's a simpler example that I'm trying and it does nothing:
>
> Assuming[x^2 + x == h, (x^2 + x)^2+h] // FullSimplify
>
> Is there a way to make this work?
>
> Thanks!
>
>
> --
>
> Bob Hanlon
>
>



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