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# asin

Arc sine function
View other versions (4)

## Interface

#include <math.h>double asin (double x)long asinl (long double x)float asinf (float x)#include <complex.h>complex asin (complex x)double complex casin (complex x)float complex casinf (float complex x)long double complex casinl (long double complex x)

## Description

The asin function computes the principal value of the arc sine of x in the range $\inline&space;[-1,1]$, returning a value in the interval $\inline&space;[-\pi/2,+\pi/2]$. The arc sine is also often called the inverse sine and is denoted by $\inline&space;\sin^{-1}(x)$.

The complex inverse sine is defined by:
$\mathrm{asin}(x)&space;=&space;-i&space;\log\left&space;(i&space;x&space;+&space;\sqrt{1-x^2}&space;\right&space;)$

Example:
##### Example - Arc sine function
Workings
#include <stdio.h>
#include <math.h>
int main(void)
{
double result, x = 0.289;
result = asin(x);
printf("The arc sin of %lf is %lf\n", x, result);
return 0;
}
Solution
Output:

The arc sin of 0.289000 is 0.293182

## Special Values

asin ( 0 ) returns 0.

asin ( x ) returns a NaN and raises the invalid floating-point exception for |x| > 1.

## Standards

The asin function conforms to ISO/IEC 9899:1999(E).

## Compatibility

DOSUNIXWindowsANSI CC++ only
asinl
asinf
Real asin
Complex asin
Complex casin