[TubaMorg]

I would like to suggest, without actually knowing your specific application, that you might want to utilize a lookup table. If it is a situation where you need to do the calculations many, many times, then a lookup table will save you computation time as trig functions do have some overhead. Precalculate your trig function for, say, 0-359 degrees and plug the values into an array (indexed 0-359 of course!). Then when needed you just index the array for the answer. If this is a navigation application 0-359 degrees should really be enough resolution, given the error inherent in the sensors. The only drawback is, of course, you have to use up memory to store the array of floats.