C language hacking
Doug Gwyn <gwyn>
gwyn at brl-tgr.ARPA
Fri Nov 16 23:55:00 AEST 1984
>> It would also be nice if sin( x ) and cos( x ) could be
>> computed simultaneously with reduced cost. I doubt if this is
>> possible but would like to know if it is.
> sine = sin(x);
> cosine = sqrt(1.0 - sine*sine);
I wish people would check things out before posting them. On our
4.2BSD system, the sqrt() approach is actually SLOWER than using
cos(). (Under UNIX System V it is very slightly faster.) Now,
if I wanted cos(x)^2, I would certainly use 1 - sin(x)^2, which
I already knew about (I too went to high school).
What I had in mind was more along the lines of a CORDIC algorithm
or some other obscure but useful approach.
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