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× C++ Standard Library C++ STL Library


The C++ cmath atan2() function is used to return the angle theta from the conversion of rectangular coordinates (x, y) to polar coordinates (r, theta). The return value will be in the range -𝜋 through 𝜋.

Syntax

double atan2 (double y, double x);
float atan2 (float y, float x);
long double atan2 (long double y, long double x);
double atan2 (double y, double x);
float atan2 (float y, float x);
long double atan2 (long double y, long double x);
// additional overloads
double atan2 (Type1 y, Type2 x);              

Parameters

y Specify the ordinate coordinate.
x Specify the abscissa coordinate.

Return Value

Returns theta of the point (r, theta) in polar coordinates that corresponds to the point (x, y) in Cartesian coordinates.

Example:

In the below example, atan2() function is used to calculate the theta of a point.

#include <iostream>
#include <cmath>

using namespace std;
 
int main () {
  cout<<atan2(10, 10)<<"\n";
  cout<<atan2(20, 10)<<"\n";
  cout<<atan2(-20, 10)<<"\n"; 
  return 0;
}

The output of the above code will be:

0.785398
1.10715
-1.10715

❮ C++ <cmath> Library