RE: Is -1^(2/5) really undefined in R?

*To*: mathgroup at smc.vnet.net*Subject*: [mg69105] RE: [mg69075] Is -1^(2/5) really undefined in R?*From*: "Jaccard Florian" <Florian.Jaccard at he-arc.ch>*Date*: Wed, 30 Aug 2006 06:33:09 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hello Ben, I suppose you ment (-1)^(2/5) ? If yes, I'm afraid your equalities are wrong. 1^(2/5)=1, But (-1)^(2/5)=(1*E^(I*Pi))^(2/5)=(1^(2/5))*E^(I*2*Pi/5)=E^(2IPi/5)=Cos[2Pi/5]+I*Sin[2Pi/5] Is a complex number! Regards Florian Jaccard florian.jaccard at he-arc.ch -----Message d'origine----- De : Ben [mailto:ben.carbery at spam.me] Envoyé : mardi, 29. août 2006 10:48 À : mathgroup at smc.vnet.net Objet : [mg69075] Is -1^(2/5) really undefined in R? Is -1^(2/5) really undefined in R? Mathematica seems to think so, I guess since it looks like a negative square root, but -1^(2/5) = (-1^2)^(1/5) = 1^(1/5) = 1 Is this correct mathematically? cheers, BC