RE: problem of evaluating SQRT
- To: mathgroup at smc.vnet.net
- Subject: [mg28007] RE: [mg27981] problem of evaluating SQRT
- From: "David Park" <djmp at earthlink.net>
- Date: Wed, 28 Mar 2001 02:40:35 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Would you expect your expression to be zero if x was negative? The answer depends upon the sign of x. Mathematica will simplify if you specify the sign. Simplify[Sqrt[x^2] - x, x > 0] 0 Simplify[Sqrt[x^2] - x, x < 0] -2 x David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ > From: Pek [mailto:phsoh at alum.mit.edu] To: mathgroup at smc.vnet.net > > 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 > >