C library function atan2() usage and example

C Standard Library - <math.h>

C library function double atan2(double y, double x) Returns the value in radians y/x The sign of y and x determines the correct quadrant.

Declaration

The following is atan2() function declaration.

double atan2(double y, double x)

Parameters

• x 　-- Represents the floating-point value of the x-axis coordinate.

• y 　-- Represents the floating-point value of the y-axis coordinate.

Return value

This function returns y in radians./The inverse tangent of x, the radian interval is [-pi,+pi].

Online example

The following example demonstrates atan2() function usage.

#include <stdio.h>
#include <math.h>
#define PI　3.14159265
int main ()
{
　　　double x, y, ret, val;
　　　x =　-7.0;
　　　y =　7.0;
　　　val =　180.0　/　PI;
　　　ret = atan2　(y,x)　*　val;
　　　printf("x = %lf, y = %lf 的反正切", x, y);
　　　printf("Is %lf degrees\n", ret);
　　
　　　return(0);
}

Let's compile and run the above program, which will produce the following result:

x =　-7.000000, y =　7The arctan of .000000 is　135.000000 degrees

C Standard Library - <math.h>