asin, asinf, asinl - arc sine function

Syntax	#include <math.h> double asin(double x); C11 float asinf(floatx); long double asinl(long double x); (End)
Description	These functions are the inverse function of the corresponding  sin()-functions. They return the principal value (i.e. corresponding angle in radians) of the arc sine of a floating-point number x in the range [-1.0, +1.0].
Return val.	arc sine(x)	if successful. A floating-point number of type double in the range [-pi/2, +pi/2] is returned.
	0.0	for values of x that are not in the range [-1.0, +1.0]. errno is set to indicate the error.
	0.0	if the result causes an underflow.
Errors	asin(), asinf() and asinl() will fail if: EDOM        The value of x is not in the range [-1.0, +1.0].
Notes	To be sure of catching an error, you should set errno to 0 before calling asin(). If after execution errno != 0, an error has occurred.
See also	acos(), atan(), atan2(), cos(), sin(), tan(), math.h.