How do you do a cosine regression on a graphic calculator?

I don't believe the graphic calculator has a cosine regression tool, but if you go to STAT, and CALC, there is a sin regression tool. If you hit enter on that then insert your L values, it will come up with a sin regression. The sin regression should be the same as a cosine regression, except that the sin regression should have a different value of C, usually getting rid of the value of C altogether will give you the correct regression.