My guess would be some version of the "CORDIC algorithm."
One of many search hits:
http://www.dspguru.com/info/faqs/cordic2.htm (See 2.1)

http://www.andraka.com/cordic.htm
etc..
--
Dana DeLouis
Windows XP & Office 2003


"Bernard Liengme" wrote in message
...
My bet is that Excel uses a series expansion
sin(x) = x -x^3/3! + x^5/5! - x^7/7! ...

Google on binomial, Taylor and Maclaurin series to learn more (or read a
math textbook)
best wishes

--
Bernard V Liengme
www.stfx.ca/people/bliengme
remove caps from email

"Kokopeelle" wrote in message
...
I have been studing the early formation fo trig tables by Ptolemy abotu
100-200Ad. I now would like to know the methodolgy tht ecel uses for
calculating these functions. I'm not interested in the detailed code,
just
the general methods.

Can anyone help?
--
rk koko pele