# 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 between [-1, 1].

Syntax:

```double asin(double k)

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

 `// 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; ` `    ``ret = ``asin``(k); ` `    ``val = (ret * 180) / PI; ` `    ``cout << ``"The arcsine of "` `<< k ` `         ``<< ``" is "` `<< ret << ``" radians and "` `         ``<< val << ``" degrees"``; ` ` `  `    ``return` `0; ` `} `

Output:

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

atan()

atan() function is used to find the arc tangent of a number means give a tangent value to this function it will return the angle in radian corresponding to that value. arc tangent is the inverse operation of tangent. This function accepts all real numbers.

Syntax:

```double atan(double k)

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

 `// 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 and "` `         ``<< val << ``" degrees"``; ` ` `  `    ``return` `0; ` `} `

Output:

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

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