asin - arc sine function
double asin(double x);
The asin() function calculates the arc sine of x; that is
the value whose sine is x. If x falls outside the range -1
to 1, asin() fails and errno is set.
The asin() function returns the arc sine in radians and the
value is mathematically defined to be between -PI/2 and PI/2
EDOM x is out of range.
SVID 3, POSIX, BSD 4.3, ISO 9899
acos(3), atan(3), atan2(3),