Library Function atan2 in Math Class

January 31, 2023

Library Function atan2 of math.h Header File in C

On this page we will discuss about library function atan2 in math class which is used in C.
The C header file math.h contains the standard math library functions that can be used for performing various mathematical operations. The atan2 function returns the arc tangent of yx \frac{y}{x} in radians.
Library Function atan2 in Math Class

Library Function atan2 in Math class used in C

In C programming language the atan2 function is included in math.h header file.

The range of input arguments which are passed to atan2 function can be either a positive or a negative number and returns the arc tangent of parameter yx \frac{y}{x} in radians.

Declaration of atan2 function

double atan2(double y, double x);

Parameters of atan2 function

The atan2 function accepts two input arguments of double type as given below:

ParameterDescription
x axisThis parameter is represented by x coordinate at input point of type double.
y axisThis parameter is represented by y coordinate at input point of type double.

Return value of atan2 function

The atan2  function returns a value in radians and it’s type is double. The function return value lies in the range of [−Π,Π]\left [ -\Pi,\Pi \right ] radians.

ParameterReturn Value
x>0,y>0  or  x<0,y<0x> 0,y> 0\; or\; x<0,y< 0 It returns the value between −Π  and  Π-\Pi\; and\; \Pi of type double.
x=0, y=0The function will return a domain error.
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Implementation of Library Function math.h atan2

Example 1:

The following code shows the use of atan2 function.
Run 
#include <stdio.h>
#include <math.h>
#define PI 3.141592654

int main()
{
    double number = 3.0;
    double return_value;

    return_value = atan(number);

    printf("Inverse of tan(%.2f) function = %.2f in radians", number, return_value);

    // Converting radians to degrees
    return_value = (return_value * 180) / PI;
    printf("\nInverse of tan(%.2f) function = %.2f in degrees", number, return_value);

    return 0;
}

Output:

The arc tangent of -12.5 and 4.6 is 160.0 degrees.

Example 2:

The following code shows use of atan2 function when inputs are entered by user.
Run 
#include <stdio.h>
#include <math.h>
#define PI 3.141592654

int main()
{
   /* Define temporary variables */
  double variable1, variable2, result;
  
  /* Assign the two values to variables to find the atan2 of */
  printf("Enter the value of variable1: ");
  scanf("%lf", &variable1);
  printf("Enter the value of variable2: ");
  scanf("%lf", &variable2);

  /* Calculate the Arc Tangent of value1 and value2 */
  result = atan2(variable2, variable1);
  
  /* Converting radians to degrees */
  result = result * 180.0/PI;

  /* Display the result of the calculation */
  printf("The arc tangent of %.1lf and %.1lf is %.1lf degrees.", variable1, variable2, result);
  return 0;
}

Output:

Enter the value of variable1: 6.78
Enter the value of variable2: -13.5
The arc tangent of 6.8 and -13.5 is -63.3 degrees.

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