Re: problem of evaluating SQRT
- To: mathgroup at smc.vnet.net
- Subject: [mg28019] Re: problem of evaluating SQRT
- From: "John Doty" <jpd at w-d.org>
- Date: Wed, 28 Mar 2001 02:40:49 -0500 (EST)
- Organization: Wampler-Doty Family
- References: <99pd51$leb@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <99pd51$leb at smc.vnet.net>, "Pek" <phsoh at alum.mit.edu> wrote: > Below we expect the result to be zero but it isn't. How can we get the > correct answer in this case? > > In[2]:= Sqrt[x^2] - x It's only zero for some values of x (try x->-1 if you don't believe me). Therefore Mathematica cannot reduce it automatically. To get it to do what you want, you can use either PowerExpand[] or Simplify[] with some appropriate assumption (like x>0). -- | John Doty "You can't confuse me, that's my job." | Home: jpd at w-d.org | Work: jpd at space.mit.edu