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## C++ acos()

Last Updated on Wednesday 5th Oct 2022

## acos domain

The C++ `acos()` function returns the the inverse cosine of a number in radians. It is defined in <cmath> header file.

#### Syntax

```			```
acos(x);

```

```

#### Parameters

The `acos()` function takes a one argument in the range `[-1, 1]`, means the value of cosine is in the range of `1` and `-1`.

### acos

#### Return value

The argument is in the range [-1, 1],

• `acos()` function returns the value in the range of `[0, π]`.

## std acos

#### acos() prototype [As of C++ 11 standard]

```			```
double acos(double x);
float acos(float x);
long double acos(long double x);
double acos (T x); // For integral type

```

```

#### Example 1: C++ acos()

```			```
#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main () {
double param, result;
param = 0.1;
result = acos(param) * 180.0 / PI;
printf ("The arc cosine of %f is %f degrees.\n", param, result);
return 0;
}

```

```

Output

```			```
The arc cosine of 0.100000 is 84.260830 degrees.

```

```

### acos function

#### Example 2 : C++ acos() ( Argument greater than 1 )

If the argument is greater than `1` or less than `-1`, `acos()` returns NaN i.e. not a number.

```			```
#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main () {
double param, result;
param = 4.4;
result = acos(param) * 180.0 / PI;
printf ("The arc cosine of %f is %f degrees.\n", param, result);
return 0;
}

```

```

Output

• The Above Code returns NaN (Not a Number)
```			```
The arc cosine of 4.400000 is nan degrees.

```

```