atan2

The C++ atan2() function returns the inverse tangent of a coordinate in radians. It is defined in <cmath> header file. Mathematically, atan2(y, x) = tan-1(y/x)

Syntax

			
					atan2(double y, double x);

Parameters

The atan2() function takes the x and y parameters:

x - It represents the proportion of x-coordinate (floating-point number)
y - It represents the proportion of y-coordinate (floating-point number)

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 prototype [As of C++ 11 standard]

			
					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);

atan2 function

Example 1: C++ atan2()

			
					#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main () {
  double x, y, result;
  x = -44.0;
  y = 44.0;
  result = atan2 (y,x) * 180 / PI;
  printf ("The arc tangent (%f, %f) is %f degrees\n", x, y, result );
  return 0;
}

Output

			
					The arc tangent (-44.000000, 44.000000) is 135.000000 degrees

atan2 math

Example 2 : C++ atan2() with different types

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

int main() {
  double result;
  float x = -44.6;
  int y = 4;
  result = atan2(y, x);
  cout << "atan2(y/x) = " << result << " radians" << endl;
  // Result in degrees
  cout << "atan2(y/x) = " << result * (180 / PI) << " degrees";

  return 0;
}

Output

			
					atan2(y/x) = 3.05215 radians
atan2(y/x) = 174.875 degrees

References

C++ atan2()