Re: Erf[InverseErf] -- making a function and its inverse cancel

*To*: mathgroup at smc.vnet.net*Subject*: [mg69015] Re: Erf[InverseErf] -- making a function and its inverse cancel*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Sat, 26 Aug 2006 04:40:05 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <ecoq4t$35n$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

mktippett at gmail.com wrote: > How can I get an expression like Erf[InverseErf[0,1/3]] to simplify to > 1/3? > > Cos[ArcCos[1/3]] gives 1/3. Is there some assumption that I'm missing? > > thanks, > Mike > For reason of efficiency, Mathematica does not call systematically the simplification rules. You must nudge Mathematica to force the simplification. In[1]:= FullSimplify[Erf[InverseErf[0, 1/3]]] Out[1]= 1 - 3 In[2]:= N[Erf[InverseErf[0, 1/3]]] Out[2]= 0.333333 HTH, Jean-Marc