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Re: Replace not spotting a replacement

• To: mathgroup at smc.vnet.net
• Subject: [mg103425] Re: [mg103399] Replace not spotting a replacement
• From: Adriano Pascoletti <adriano.pascoletti at dimi.uniud.it>
• Date: Mon, 21 Sep 2009 05:51:29 -0400 (EDT)
• References: <200909201021.GAA24204@smc.vnet.net>

Examine

Sqrt[2 \[Pi]] \[Tau]^(3/2) // TreeForm

and

Sqrt[ 2 \[Pi] \[Tau]] //TreeForm

to realize why no replacement is performed.


This does what you want:

In[1]:= Sqrt[2*Pi]*\[Tau]^(3/2) /. Sqrt[2*Pi] -> \[Mu]/\[Tau]^(1/2)

Out[1]= \[Mu]*\[Tau]


Adriano Pascoletti


2009/9/20 claranet news <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.
>
>
>

• References:
  • Replace not spotting a replacement
    • From: "claranet news" <david@carter-hitchin.clara.co.uk>