Re: Bug in Tanh[x]

*To*: Barry Merriman <barry at math.ucla.edu>*Subject*: Re: Bug in Tanh[x]*From*: ags at seaman.cc.purdue.edu (Dave Seaman)*Date*: Fri, 01 Mar 91 15:35:53 -0800*Cc*: mathgroup at yoda.ncsa.uiuc.edu*In-reply-to*: Your message of Wed, 27 Feb 91 19:07:15 -0800. <9103010544.AA15552@yoda.ncsa.uiuc.edu>

Someone must have found this bug previously, but there is a nasty bug in Tanh[x] (in version 1.* on a NeXT). Just try Plot[Tanh[x],{x,-3,3}] to _see_ what I mean. (I always though tanh(x) was continuous :-) Fortunately, its easy to write your own "tanh[x]": tanh[x_] := (Exp[x] - Exp[-x])/(Exp[x] + Exp[-x]) which works fine. NeXT 1.2 (Januuary 20, 1990) I tried this using Mathematica 1.2 on a NeXT (under 1.0) and I see no problem. The two plots are identical (both nicely continuous). Dave Seaman