C++ cos()

The cos() function in C++ returns the cosine of an angle (argument) given in radian.

This function is defined in <cmath> header file.


[Mathematics] cos x = cos(x) [In C++ Programming]

cos() prototype (As of C++ 11 standard)

double cos(double x);
float cos(float x);
long double cos(long double x);
double cos(T x); // Here, T is an integral type.

cos() Parameters

The cos() function takes a single mandatory argument in radians.


cos() Return value

The cos() function returns the value in the range of [-1, 1]. The returned value is either in double, float, or long double.


Example 1: How cos() works in C++?

#include <iostream>
#include <cmath>

using namespace std;

int main()
{
  double x = 0.5, result;
  
  result = cos(x);
  cout << "cos(x) = " << result << endl;
  
  double xDegrees = 25;
  
  // converting degrees to radians
  x = xDegrees*3.14159/180;
  result = cos(x);
  
  cout << "cos(x) = " << result << endl;

  return 0;
}

When you run the program, the output will be:

cos(x) = 0.877583
cos(x) = 0.906308

Example 2: cos() function with integral type

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

int main()
{
  int x = 1;
  double result;

  // result is in double
  result = cos(x);
  cout << "cos(x) = " << result << endl;
  
  return 0;
}

When you run the program, the output will be:

cos(x) = 0.540302