You can use a similar method to what Kevin uses, but replace the data with the appropriate trig function. If you know your trig identities you might be able to use his functions to get the data you need.
However, depeding on how many calculations you are doing, you should be fine with a call to arccos() from <math.h>. Consider posting the code.
BTW, I don't
think squaring is nearly as processor intensive as the other functions.
See also:
http://en.wikipedia.org/wiki/CORDIC
http://en.wikipedia.org/wiki/Generat...ometric_tables