 # C asin()

The asin() function defined in the math.h header file. It helps to return the arc sine value of the given number in radians. The arc sine means inverse sine value.

``````
double asin(double x); #where x can be in int, float or long double
```
```

Also, two functions asinf() and asinl() were used with type float and long double respectively.

``````
float asinf(float x);
long double asinl(long double x);
```
```

## asin() Parameters:

The asin() function takes a single parameter between the range 1 ≥ x ≥ -1. Using cast operator we can explicitly convert the type to double to find the arc sine of type int, float, or long double.

Parameter Description Required / Optional
double value A double value between - 1 and +1 Required

## asin() Return Value

The return value of asin() function is in the range of [-π/2, +π/2]  in radians.

Input Return Value
x = [-1, +1] [-π/2, +π/2] in radians
-1 > x or x > 1 NaN (not a number)

## Examples of asin()

### Example 1: Working of asin() function in C?

``````
#include <stdio.h>
#include <math.h>
int main()
{

const double PI =  3.1415926;
double v, output;

v =  -0.5;
output = asin(v);
printf("The Inverse of sin(%.2f) = %.2lf in radians\n", v, output);

//radians to degree convertion
output = asin(v)*180/PI;
printf("The Inverse of sin(%.2f) = %.2lf in degrees\n", v, output);

// paramter not in range
v = 1.2;
output = asin(v);
printf("The Inverse of sin(%.2f) = %.2lf", v, output);

return 0;
}
```
```

Output:

```
The Inverse of sin(-0.50) = -0.52 in radians
The Inverse of sin(-0.50) = -30.00 in degrees
the Inverse of sin(1.20) = nan
```

### Example 2: How asinf() and asinl() functions worked in C?

``````
#include <stdio.h>
#include <math.h>
int main()
{
float f, fsinx;
long double l, lsinx;

// type float
f = -0.505405;
fsinx = asinf(f);

//type long double
l = -0.50540593;
lsinx = asinl(l);

printf("asinf(x) is equal to %f in radians\n", fsinx);
printf("asinl(x) is equal to %Lf in radians", lsinx);

return 0;
}
```
```

Output:

```
asinf(x) is equal to -0.529851 in radians
asinl(x) is equal to -0.529852 in radians
```
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