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