Re: Simple question about inverse of a function

*To*: mathgroup at smc.vnet.net*Subject*: [mg122538] Re: Simple question about inverse of a function*From*: Simon <simonjtyler at gmail.com>*Date*: Mon, 31 Oct 2011 06:52:02 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j8j5ci$f6v$1@smc.vnet.net>*Reply-to*: comp.soft-sys.math.mathematica at googlegroups.com

Inverse functions works on functions, not on the function evaluated at some point. So you want f[t_] := (1 - t)^theta finv = InverseFunction[f] (* Returns: 1 - #1^(1/theta) & *) InverseFunction does not check the possible branch structure of the function, so for non-built-in it gives the warning "Inverse functions are being used. Values may be lost for multivalued inverses." You can check that things are ok using Reduce, or in your case FullSimplify[f[finv[t]] == t, theta >= 1] (* Returns: True *)