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MathGroup Archive 2007

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73941] Re: Problems with simplify and Sqrt[a^2]
  • From: Bhuvanesh <lalu_bhatt at yahoo.com>
  • Date: Sat, 3 Mar 2007 01:13:31 -0500 (EST)

Sqrt[a^2] is equal to a only for Re[a]>0; for Re[a]<0 it is -a. So Mathematica is being careful and not making assumptions that could end up giving a wrong result. You can get what you want by using PowerExpand.

In[1]:= PowerExpand[v3/Sqrt[v1^2]/Sqrt[v2^2] - v3/v1/v2]

Out[1]= 0

Another way is to use Simplify (or FullSimplify) with assumptions: Simplify[expression, v1>0 && v2>0 && ...]

Bhuvanesh,
Wolfram Research.


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