c/numeric/math/cospi

@1-6@ Computes the cosine of measured in radians, thus regarding  as a measurement in half-revolutions. @7@ Type-generic macro: calls the correct function based on the type of. If the argument has integer type,  is called.

Return value
If no errors occur, the cosine of ($cos(π&times;arg)$) in the range $[-1, +1]$, is returned.

Error handling
Errors are reported as specified in.

If the implementation supports IEEE floating-point arithmetic (IEC 60559):
 * if the argument is ±0, the result is ;
 * if the argument is ±∞, NaN is returned and fe_invalid is raised;
 * if the argument is NaN, NaN is returned.