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Re: Replace not spotting a replacement

  • To: mathgroup at smc.vnet.net
  • Subject: [mg103583] Re: [mg103399] Replace not spotting a replacement
  • From: "David Carter-Hitchin" <david at carter-hitchin.clara.co.uk>
  • Date: Tue, 29 Sep 2009 07:37:53 -0400 (EDT)
  • References: <22608339.1253442945257.JavaMail.root@n11> <003001ca39e9$96f2d3e0$c4d87ba0$@net>

Thanks, David,

Same solution, but simpler than Bob's.

Regards,
David.

> -----Original Message-----
> From: David Park [mailto:djmpark at comcast.net]
> Sent: 20 September 2009 12:58
> To: 'claranet news'; mathgroup at smc.vnet.net
> Subject: RE: [mg103399] Replace not spotting a replacement
> 
> Replace does not Solve or do algebra. Replace only matches a pattern
> and
> that pattern does not occur in your expression.
> 
> Solve for Tau in terms of Mu and then replace.
> 
> Sqrt[2 \[Pi] \[Tau]] == \[Mu]
> \[Tau]sol = Part[Solve[%, \[Tau]], 1, 1]
> Sqrt[2 \[Pi]] \[Tau]^(3/2) /. \[Tau]sol
> 
> 
> David Park
> djmpark at comcast.net
> http://home.comcast.net/~djmpark/
> 
> 
> From: claranet news [mailto:david at carter-hitchin.clara.co.uk]
> 
> 
> Hi Folks,
> 
> Seems the replace function is being a bit dim here.  This fails:
> 
> Sqrt[2 \[Pi]] \[Tau]^(3/2) /. Sqrt[ 2 \[Pi] \[Tau]] -> \[Mu]
> 
> Apologies if this is an FAQ - I couldn't see anything about it.  What
> do I
> need to do here to coerce Mathematica into making this replacement? I
> tried
> using the
> Collect function on tau first, but that didn't seem to work.  I also
> tried
> re-writing the replacement rule as
> 
> Sqrt[2 \[Pi]] \[Tau]^(3/2) /. Sqrt[ 2 \[Pi] ] t^(1/2) -> \[Mu]
> 
> But still no joy.
> 
> Anyone know?
> 
> Many thanks,
> David.
> 
> 
> 
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