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From: madler@pooh.caltech.edu (Mark Adler)
Newsgroups: comp.sys.next
Subject: Re: NeXT Mathematica Bug
Keywords: Math Bug
Message-ID: <1991Mar6.001811.18777@nntp-server.caltech.edu>
Date: 6 Mar 91 00:18:11 GMT
References: <1991Mar3.053006.2986@math.ucla.edu> <1991Mar4.035543.19802@wam.umd.edu> <1991Mar5.181203.11715@wam.umd.edu>
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Organization: California Institute of Technology, Pasadena
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In article <1991Mar5.181203.11715@wam.umd.edu> charlie@wam.umd.edu (Charles William Fletcher) writes:
>Related-I plotted tanh(x) using Gnuplot 2.02 compiled under 1.0.
>There was no problem-it correctly plotted. I'm not sure why this
>happens unless Gnuplot keeps all its math functions internal. Mark ....?

Hi.  Yeah, it's because gnuplot uses sinh() and cosh() to compute tanh(),
and that bypasses the FTANH bug in 2.0.  Why do they use sinh() and cosh()
you ask?  (I knew you would.)  Because the operations in gnuplot work on
complex numbers as well, and it is easiest to write tanh(z) in terms of
the real functions sinh(), cosh(), sin(), and cos().

Mark Adler
madler@pooh.caltech.edu