atan2 in c programming

## What is atan2 in c programming?

atan2 in c is used to find arc tangent in radians of y/x based on signs of both values that determine the correct quadrant.

It is defined in math.h header file.

### Prototype

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

### Parameter

This function takes two floating point values as x and y co-ordinate values.

### Return value

This function returns arc tangent of y/x ,in the interval [-pi,+pi] radians.

## Example program for atan2 in c

``````#include<stdio.h>
#include<math.h>
#define PI 3.14
int main()
{
double x=4.0,y=5.0,res,val;
val=180.0/PI;
res=atan2(y,x)*val;
printf("The arc tangent value is %lf \n",res);
return 0;
}``````

``gcc file_name.c -lm``

### Code explanation

atan2 function is called by passing x and y values to it. The result is multiplied to get the arc tangent value in radians. The result is printed onto the console.

atan2() Man page

## Difference between atan2 and atan in c

atan2 in c is used to find arc tangent in radians of y/x based on signs of both values that determine the correct quadrant. atan in c is a mathematical function that is used to find the arc tangent value of a given number in radians.

atan2 takes two input parameters as x and y co-ordinates. atan takes one input parameter.

Prototypes are as follows

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

double atan(double y);``````