# C++ Math cos() function

In this post today I am going to discuss C++ Math cos() functions.

The function is used to determine the cosine of an angle given in terms of a radian.

## Syntax Of cos() function:

Consider a radian ‘x’. The syntax would be:

``````float cos(float x);
float cos(double x);
float cos(long double x);
double cos(integral x);``````

### Parameter:

x: Value specified in terms of a radian.

### Return value:

It returns the cosine of an angle in the range of[-1,1].

Example-1:

Let’s look at a basic case where x is positive.

```#include <iostream>
#include<math.h>
using namespace std;
int main()
{
double degree=60;
double d=60*3.14/180;
cout<<"Cosine of an angle is : "<<cos(d);
return 0;
}  ```

Output:

``````Cosine of an angle is : 0.50046
``````

When the degree is equal to60, the cos() function calculates the cosine of an angle.

Example-2:

Let’s look at a basic case where x is negative.

```#include <iostream>
#include<math.h>
using namespace std;
int main()
{
double degree= -90;
cout<<"Cosine of an angle is :"<<cos(radian);
return 0;
}  ```

Output:

``````Cosine of an angle is :0.000796327
``````

When the number is negative, the cos() function determines the cosine of the angle, but it stays the same as cos(-x) =cos (x).