Re: Pi day

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#79

From: Glenn Baddeley
Date: Fri, 04 Apr 1997 00:00

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Chris Dearlove wrote:
> A colleague described to me once a problem he once found (in someone
> else's code, and not while he worked here) where pi had been accidentally
> coded to too few places. (In some Fortran - all the places were there,
> the "D0" after the "3.1415926535..." was missing). This caused a noticeable
> ripple (maybe 140 dB down) when numerically simulating a signal of some
> sort. This was sufficiently large to matter.
> 
> Of course here just a few more digits would have been enough, maybe 10
> would have done. (I have seen cases where a few more than that are a
> good idea in general precision requirements.)

Pi as a constant in a program can be accurately assigned during
initialisation by calculation rather than coding the digits.

eg.  Pi = arctan(1) * 4

Just make sure the real precision of the variable and arctan
function is sufficient.

eg. In Visual Basic

dim Pi as double

Pi = atn(1) * 4

Print Pi

 3.14159265358979 

This is the atn() example in the Language Reference book!

HTH,
Glenn.

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From: Glenn Baddeley <gbaddele@vitgssw.telecom.com.au>
Subject: Re: Pi day
Date: 1997/04/04
Message-ID: <3345643F.3D51@vitgssw.telecom.com.au>
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