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From: mjo@ttardis.UUCP (Mike O'Connor)
Newsgroups: comp.edu,sci.math,sci.misc
Subject: Re: Cosine of Pi/2.0  (was: Subtle Math Questions)
Message-ID: <2734@ttardis.UUCP>
Date: 27 Apr 91 16:16:07 GMT
Organization: Artificial Intelligence Society
Lines: 26

In article <22614@lanl.gov>, jlg@cochiti.lanl.gov (Jim Giles) writes:

>In 'radians' mode:
>The calculator is just being honest.  There is no representable
>number which is exactly equal to pi/2.  This means that there is
>no representable number for which the cosine is exactly zero.
>This is one of the first tests I make of a calculator: if it gives
>zero for cosine of _anything_ that can be represented, it probably
>has a bad cosine function.

What other calculators have you found this "honesty" on, out of curiosity?

Most of the cheapo scientific calculators I have will output 0 for 
cos of pi/2.

I wouldn't necessarily see this as a big problem...  depends on the kind
of accuracy expected of you.



					...Mike

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