# asin() and atan() functions in C/C++ with Example

In C++, asin() and atan() is a predefined function used for mathematical calculations. math.h is the header file required for various mathematical functions. All the functions available in this library take double as an argument and return double as the result.

asin()

asin() function is used to find the arc sine of a number means give a sin value to this function it will return the angle in radian corresponding to that value. In trigonometrics, arc sine is the inverse operation of sine.
Note: The argument passed to this function must be in the range of [-1, 1] and asin() function returns the values in the range of [-?/2, ?/2].
Syntax:

```double asin(double k)

Parameters:
k is the value whose corresponding angle we have to find. ```

## CPP

 `// CPP code to illustrate` `// the use of asin function` `#include ` `using` `namespace` `std;`   `#define PI 3.14159265`   `int` `main()` `{` `    ``double` `k, ret, val;`   `    ``// Take any value between [-1, 1]` `    ``k = 0.5;` `    ``// asin() returns value in the range of [-?/2,?/2]` `    ``ret = ``asin``(k);` `    ``val = (ret * 180) / PI;` `    ``cout << ``"The arcsine of "` `<< k << ``" is "` `<< ret` `         ``<< ``" radians or "` `<< val << ``" degrees"``;`   `    ``return` `0;` `}`

Output:

`The arcsine of 0.5 is 0.523599 radians or 30 degrees `

atan()

atan() function is used to find the arc tangent of a number means gives a tangent value to this function it will return the angle in radians corresponding to that value. arc tangent is the inverse operation of tangent. This function accepts all the real numbers and atan() function returns the values in the range of [-?/2, ?/2].
Syntax:

```double atan(double k)

Parameters:
k is the value whose corresponding angle we have to find.
```

## CPP

 `// CPP code to illustrate` `// the use of atan function` `#include ` `using` `namespace` `std;`   `#define PI 3.14159265`   `int` `main()` `{` `    ``double` `k, ret, val;`   `    ``// Take any value` `    ``k = 1.0;` `    ``ret = ``atan``(k);` `    ``val = (ret * 180) / PI;` `    ``cout << ``"The arctangent of "` `<< k << ``" is "` `<< ret` `         ``<< ``" radians or "` `<< val << ``" degrees"``;`   `    ``return` `0;` `}`

Output:

`The arctangent of 1 is 0.785398 radians or 45 degrees `

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