# asin() function with example in C++

C++ asin() function: Here, we are going to learn about the asin() function with example of cmath header in C++ programming language?
Submitted by IncludeHelp, on April 28, 2019

## C++ asin() function

asin() function is a library function of cmath header, it is used to find the principal value of the arc sine of the given number, it accepts a number (x) and returns the principal value of the arc sine of x in radians.

Note: Value (x) must be between -1 to +1, else it will return a domain error (nan).

Syntax of asin() function:

```    asin(x);
```

Parameter(s): x – is the value whose arc sine to be calculated.

Return value: double – it returns double type value that is the principal value of the arc sine of the given number x.

Example:

```    Input:
float x = 0.65;

Function call:
asin(x);

Output:
0.707584
```

### C++ code to demonstrate the example of asin() function

```// C++ code to demonstrate the example of
// asin() function

#include <iostream>
#include <cmath>
using namespace std;

// main() section
int main()
{
float x;

x = -1.0;
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

x = -0.89;
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

x = 0.65;
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

x = 1;
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

return 0;
}
```

Output

```asin(-1): -1.5708
asin(-0.89): -1.09735
asin(0.65): 0.707584
asin(1): 1.5708
```

Example with domain error

If we provide the value out of the range (except -1 to +1), it returns nan.

```// C++ code to demonstrate the example of
// asin() function

#include <iostream>
#include <cmath>
using namespace std;

// main() section
int main()
{
float x;

x = -0.89;  //no error
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

x = 2.65;   //error
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

x = -1.25;  //error
cout<<"asin("<<x<<"): "<<asin(x)<<endl;

return 0;
}
```

Output

```asin(-0.89): -1.09735
asin(2.65): nan
asin(-1.25): nan
```

Reference: C++ asin() function

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