RE: How do I pick out the expression under a radical?
- To: mathgroup at smc.vnet.net
- Subject: [mg36242] RE: [mg36225] How do I pick out the expression under a radical?
- From: "Florian Jaccard" <jaccardf at eicn.ch>
- Date: Wed, 28 Aug 2002 04:16:02 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Here a easy way : In[4]:= expr=a b x^2 + 5 x^3 + 5 Sqrt[4 - x^2] In[5]:= FullForm[expr] Out[5]//FullForm= Plus[Times[a,b,Power[x,2]],Times[5,Power[x,3]], Times[5,Power[Plus[4,Times[-1,Power[x,2]]],Rational[1,2]]]] In[9]:= expr[[3,2,1]] Out[9]= 4 - x^2 Meilleures salutations Florian Jaccard professeur de Mathématiques EICN-HES e-mail : jaccardf at eicn.ch -----Message d'origine----- De : Steve Beach [mailto:asb4 at psu.edu] Envoyé : mar., 27. août 2002 08:08 À : mathgroup at smc.vnet.net Objet : [mg36225] How do I pick out the expression under a radical? I'm a poor physicist trying to figure out how to sort out the "physical" from the "non-physical" solutions to a problem. To do that, I need to be able to look at an expression and pick out a subexpression, the part under the radical. For example, say I've got the expression a b x^2 + 5 x^3 + 5 Sqrt[4 - x^2] I'd like to pick out "4 - x^2", which would then tell me that x is between +/- 2. I know there has got to be an easy way to do it, but I can't find it. Any help would be appreciated. Thanks, Steve Beach asb4 at psu.edu http://www.thebeachfamily.org