Header File 

math.h  

Category 

Math Routines 

Prototype 

double asin(double x); 

long double asinl(long double x); 

Description 

Calculates the arc sine. 

asin of a real argument returns the arc sine of the input value.  

asinl is the long double version; it takes a long double argument and returns a long double result. 

Real arguments to asin and asinl must be in the range -1 to 1, or else asin and asinl return NAN and set the global variable errno to 

EDOM Domain error 

Return Value 

asin and asinl of a real argument return a value in the range -pi/2 to pi/2. Error handling for these functions may be modified through the functions _matherr and _matherrl. 

Example  

#include <stdio.h>
#include <math.h>
int main(void)
{
   double result;
   double x = 0.5;
   result = asin(x);
   printf("The arc sin of %lf is %lf\n", x, result);
  return(0);
}

Portability