If the operand is outside the acceptable range, the C2 flag is set, and ST remains unchanged. It is the programmer's responsibility to reduce the operand to an absolute value smaller than 263 by subtracting an appropriate integer multiple of 2π. Refer to the Intel documentation for a discussion of the proper value to use for π in performing such reductions.
It is faster to run FSINCOS than to run both FSIN and FCOS.