Re: Different answers in mathematica and my calculator.

*To*: mathgroup at smc.vnet.net*Subject*: [mg125591] Re: Different answers in mathematica and my calculator.*From*: psycho_dad <s.nesseris at gmail.com>*Date*: Tue, 20 Mar 2012 02:21:56 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jk70c1$12t$1@smc.vnet.net>

I'm afraid that Sec corresponds to 1/Cos in the sense of 2 and 1/2 respectively. The function you want is ArcCos (inverse cosine). As for the first question, mathematica is right, so you are either doing something wrong on the calculator or it doesn't support complex numbers, as Power[2(-2)+3, (3)^-1]=(-1)^(1/3) is complex.