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# C math asin() function

### C math asin() function

The C library function double asin(double x) is used to return the arc sine (inverse sine) of any number x in radians. It takes a single argument x (1 ≥ x ≥ -1) and returns the arc sine of it in radians. This function is included in <math.h> header file.

Syntax:
`double asin(double x);`

### Parameters

x − It is the floating point value in the interval [-1,+1].

Here is an example of asin() function:
``````
// C code to illustrate
// the use of acos function
#include <stdio.h>
#include <math.h>
#define PI 3.14159265
int main ()
{
double x, ret, val;
x = 0.75;
val = 180.0 / PI;
ret = asin(x) * val;
printf("The arc sine of %lf is %lf degrees", x, ret);
return(0);
}
```
```
Output:
The arc sine of 0.750000 is 48.590378 degrees
Example-2
``````
// C code to illustrate
// the use of acos function
#include <stdio.h>
#include <math.h>
#define PI 3.14159265
int main ()
{
double x, ret, val;
x = 0.555;
val = 180.0 / PI;
ret = asin(x) * val;
printf("The arc sine of %lf is %lf degrees", x, ret);
return(0);
}
```
```
Output:
The arc sine of 0.555000 is 33.710715 degrees