atan2d

Compute the degree corresponding to the arctangent of y/x.

Interface Definition

C interface:

float atan2df(float y, float x);

double atan2d(double y, double x);

long double atan2dl(long double y, long double x);

Parameters

Parameter	Type	Description	Input/Output
x	For atan2df, x is of single-precision floating-point type. For atan2d, x is of double-precision floating-point type. For atan2dl, x is of long double-precision floating-point type.	Floating-point value of the input data.	Input
y	For atan2df, y is of single-precision floating-point type. For atan2d, y is of double-precision floating-point type. For atan2dl, y is of long double-precision floating-point type.	Floating-point value of the input data.	Input

Return Value

Normal range: The degree corresponding to the arctangent of y/x is returned, that is, atan2d(y/x) = atan2(y/x) * 180/π.

Special values: See the following table.

Input Value (y)	Input Value (x)	Output Value (result)
+0	+0	+0
+0	-0	180
+0	inf	+0
+0	-inf	180
+0	NaN	NaN
-0	+0	-0
-0	-0	-180
-0	inf	-0
-0	-inf	-180
-0	NaN	NaN
inf	+0	90
inf	-0	90
inf	inf	45
inf	-inf	135
inf	NaN	NaN
-inf	+0	-90
-inf	-0	-90
-inf	inf	-45
-inf	-inf	-135
-inf	NaN	NaN
NaN	+0	NaN
NaN	-0	NaN
NaN	inf	NaN
NaN	-inf	NaN
NaN	NaN	NaN

Dependency

C: "km.h"

Example

C interface:

// typical usage
float x1 = -1.0, x2 = 1.0, x3 = 0.5, x4 = -0.5;
// special handling
float a = 0.0, b = INFINITY, c = -INFINITY, d = NAN;
// print result
printf("atan2d(1.0, 1.0) = %.15f\n", atan2d(x1, x1));
printf("atan2d(-1.0, -1.0) = %.15f\n", atan2d(x2, x2));
printf("atan2d(0.5, 0.5) = %.15f\n", atan2d(x3, x3));
printf("atan2d(-0.5, -0.5) = %.15f\n", atan2d(x4, x4));
printf("atan2d(0.0, 0.0) = %.15f\n", atan2d(a, a));
printf("atan2d(-0.0, -0.0) = %.15f\n", atan2d(-a, -a));
printf("atan2d(INFINITY, INFINITY) = %.15f\n", atan2d(b, b));
printf("atan2d(-INFINITY, -INFINITY) = %.15f\n", atan2d(c, c));
printf("atan2d(NAN, NAN) = %.15f\n", atan2d(d, d));
/*
 *  atan2d(1.0, 1.0) = -135.000000000000000
 *  atan2d(-1.0, -1.0) = 45.000000000000000
 *  atan2d(0.5, 0.5) = 45.000000000000000
 *  atan2d(-0.5, -0.5) = -135.000000000000000
 *  atan2d(0.0, 0.0) = 0.000000000000000
 *  atan2d(-0.0, -0.0) = -180.000000000000000
 *  atan2d(INFINITY, INFINITY) = 45.000000000000000
 *  atan2d(-INFINITY, -INFINITY) = -135.000000000000000
 *  atan2d(NAN, NAN) = nan
 *
 * */

Parent topic: Function Syntax