atan2, atan2l

raw OCR

Calculates the arc tangent of ylx.

Defined in header <math.h>

Syntax

#include <math.h>
double atan2(double  y, double x);
long double atan21(long double y, long double x);

Portability

	DOS	UNIX	Windows	ANSI C	C++ only
atan2	■	■	■	■
atan2l	■		■

Remarks

atan2 returns the arc tangent of y/x; it produces correct results even when the resulting angle is near pi/2 or -pi/2 (x near 0).

If both X and y are set to 0, the function sets the global variable errno to EDOM.

atan2l is the long double version; it takes long double arguments and returns a long double result.

Return value

atan2 and atan2l return a value in the range -pi to pi.

Error handling for these functions can be modified through the functions matherr and _matherrl.

Example

#include <stdio.h>
#include <math.h>
int main(void)
{
   double result, x = 90.0, y = 15.0;
   result = atan2(y, x);
   printfC'The arc tangent ratio of %lf is %lf\n",  (y/x),   result);
   return 0;

Differences from modern implementations

Nothing recorded yet.

Modern references

These are search links, not yet checked by hand.

Stable link: /3.1/math.h/atan2/ · short form /3.1/atan2/