using cosine and sin to find missing angles

Question

how can i use cosine and sine in my iphone application to find the missing value of angles? if i have a float that contains a number, how can i get the cosine of that angle. i used this example however it gave me errors

        double x1float = (cos(pfloat));

Answer 1

What error does it give you? Did you include math.h, assuming this is C code?