In this C++ tutorial, you will learn how to find the cosine of an angle using cos() function of cmath, with syntax and examples.

## C++ cos()

C++ cos() function returns cosine of an angle (in radians). Angle is passed as an argument to cos().

## Syntax

The syntax of C++ cos() is

`cos(x)`

where

Returns

Return value depends on the type of value passed for parameter x. The return value of cos(x) is

• double if x is double.
• float if x is float.
• long double if x is long double.

The synopsis of cos() function is

```double cos(double x);
float cos(float x);
long double cos(long double x);
double cos(T x); // for integral type argument values```

cos() is a function of cmath library. Include cmath library in the program, if using cos().

## Example

In this example, we read angle value from user and find cosine of this angle using cos() function.

C++ Program

```#include <iostream>
#include<cmath>
using namespace std;

int main() {
double x;
cout << "Enter angle (in radians) : ";
cin >> x;

double result = cos(x);
cout << "cos(" << x << ") : " << result << endl;
}```

Output

```Enter angle (in radians) : 1.2
cos(1.2) : 0.362358
Program ended with exit code: 0```
```Enter angle (in radians) : 0.5
cos(0.5) : 0.877583
Program ended with exit code: 0```

## Conclusion

In this C++ Tutorial, we learned the syntax of C++ cos(), and how to use this function to find the cosine of an angle, with the help of examples.