Re: problem of evaluating SQRT
- To: mathgroup at smc.vnet.net
- Subject: [mg28015] Re: [mg27981] problem of evaluating SQRT
- From: Tomas Garza <tgarza01 at prodigy.net.mx>
- Date: Wed, 28 Mar 2001 02:40:44 -0500 (EST)
- References: <200103270626.BAA21730@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
The "correct" answer actually depends on x. If you give Mathematica no information about x, then it can go no further. You say that you expect In[1]:= Sqrt[x^2] - x Out[1]= -x + Sqrt[x^2] to be zero. But this is not the case when x<0, is it? You may supply whatever information you have in the assumptions within Simplify: In[2]:= Simplify[Sqrt[x^2] - x, x >= 0] Out[2]= 0 In[3]:= Simplify[Sqrt[x^2] - x, x < 0] Out[3]= -2 x Tomas Garza Mexico City ----- Original Message ----- From: "Pek" <phsoh at alum.mit.edu> To: mathgroup at smc.vnet.net Subject: [mg28015] [mg27981] problem of evaluating SQRT > Hi, > > We have a question of how sqrt can be evaluated. > > In[1]:= > Sqrt[x^2] > > Out[1]= > (This part is just sqrt[X^2]) > > 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 > > Out[2]= > (This part is -x + sqrt[x^2] ) > > Will really appreciate your help. Thanks. > > Pek > >
- References:
- problem of evaluating SQRT
- From: "Pek" <phsoh@alum.mit.edu>
- problem of evaluating SQRT