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Re: Problems with simplify and Sqrt[a^2]

• To: mathgroup at smc.vnet.net
• Subject: [mg73946] Re: Problems with simplify and Sqrt[a^2]
• From: Johan Grönqvist <johan.gronqvist at gmail.com>
• Date: Sat, 3 Mar 2007 01:16:11 -0500 (EST)
• References: <es907e$2b4$1@smc.vnet.net>

dshortho skrev:
> any help on this one:
> I would have thought Mathematica would have resolved Sqrt[v1^2] to v1 (!?)
> 

Test this with v1=(-1) and you will see why it does not hold.

What you may want is Sqrt[v1]^2 = v1, and mathematica does this.


> Does anyone out there know why it does not do this, as it is causing some problems with some proofs I am doing ?
> 

I think you want:

Simplify[Sqrt[x^2], Assumptions -> x>0}]