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Date: Thu, 27 Jun 2013 22:12:53 -0700
From: David Schultz <das@FreeBSD.ORG>
To: Bruce Evans <brde@optusnet.com.au>
Subject: Re: sincos?
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Cc: enh <enh@google.com>, Steve Kargl <sgk@troutmask.apl.washington.edu>,
 freebsd-numerics@freebsd.org
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Steve had some patches for this that could have been committed
years ago if people would stop quibbling about it. :)  I put it on
the TODO list on the wiki for a reason!  Merging sin() and cos()
is basically all there is to it.

The advantages to having it are:

1. It's faster when computing the sine and cosine of large angles,
   because the arg reduction only has to be done once.  In particular,
   functions like cexp() can benefit.
2. Most math libraries have it, even though it's not standardized.

The disadvantage is that someone has to spend 15 minutes writing
it, plus do some testing...