C++ atan2()

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

int main() {

  // get the value of tan-1(5.0 / 2.0)
  cout << atan2(5.0, 2.0);

  return 0;
}

// Output: 1.19029

atan2() Syntax

The syntax of the atan2() function is:

atan2(double y, double x);

atan2() Parameters

The atan2() function takes the following parameters:

• x - floating-point number that represents the proportion of the x-coordinate
• y - floating-point number that represents the proportion of the y-coordinate

atan2() Return Value

The atan2() function returns:

• a floating-point value in the range of [-π, π].
• 0 if both x and y are zero

atan2() Prototypes

The prototypes of atan2() as defined in the cmath header file are:

double atan2(double y, double x);

float atan2(float y, float x);

long double atan2(long double y, long double x);

// for combinations of arithmetic types
double atan2(Type1 y, Type2 x);

Example 1: C++ atan2()

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

int main() {
  double x = 10.0, y = -10.0;

  double result = atan2(y, x);

  // convert result to degrees
  double degree = result * (180 / 3.141592);

  cout << "atan2(y/x) = " << result << " radians" << endl;
  cout << "atan2(y/x) = " << degree << " degrees";
  
  return 0;
}

Output

atan2(y/x) = -0.785398 radians
atan2(y/x) = -45 degrees

Example 2: C++ atan2() with Different Types

In this program, we will use arguments of different data types with the atan2() function.

#include <iostream>
#include <cmath>
#define PI 3.141592654
using namespace std;

int main() {
  double result;
  float x = -31.6;
  int y = 3;
  
  // atan2() with float and int arguments
  result = atan2(y, x);
  
  cout << "atan2(y/x) = " << result << " radians" << endl;
  
  // Display result in degrees
  cout << "atan2(y/x) = " << result * (180 / PI) << " degrees";

  return 0;
}

Output

atan2(y/x) = 3.04694 radians
atan2(y/x) = 174.577 degrees