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; }

```
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; double radian=degree*3.14/180; 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).