C++ atan()

The atan() function in C++ returns the inverse tangent of a number (argument) in radians.

This function is defined in <cmath> header file.


[Mathematics] tan-1x = atan(x) [In C++ Programming];

atan() prototype [As of C++ 11 standard]

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

atan() Parameters

The atan() function takes a single mandatory argument (can be positive, negative, or zero)


atan() Return value

The atan() function returns the value in the range of [-π/2, π/2].


Example 1: How atan() works?

#include <iostream>
#include <cmath>

using namespace std;

int main()
{
  double x = 57.74, result;
  result = atan(x);
  
  cout << "atan(x) = " << result << " radians" << endl;
  
  // Output in degrees
  cout << "atan(x) = " << result*180/3.1415 << " degrees" << endl;
  
  return 0;
}

When you run the program, the output will be:

atan(x) = 1.55348 radians
atan(x) = 89.0104 degrees

Example 2: atan() function with integral type

#include <iostream>
#include <cmath>
#define PI 3.141592654

using namespace std;

int main()
{
  int x = 14;
  double result;
  
  result = atan(x);
  
  cout << "atan(x) = " << result << " radians" << endl;
  // Output in degrees
  cout << "atan(x) = " << result*180/3.1415 << " degrees" << endl;
  
  return 0;
}

When you run the program, the output will be:

atan(x) = 1.49949 radians
atan(x) = 85.9169 degrees