- NAME
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atan2 - arc tangent function of two variables.
- SYNOPSIS
#include <math.h>
double atan2(double y, double x);- DESCRIPTION
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The atan2() function calculates the arc tangent of the two variables x and y. It is similar to calculating the arc tangent of y / x, except that the signs of both arguments are used to determine the quadrant of the result. The floating-point value returned by atan2 will be a number in the range [-PI, PI].
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Warning
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You’ll also need to link the program against the math library (see example below) using the -lm compile/link option.
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- RETURN VALUE
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The atan2() function returns the result in radians, which is between -PI and PI (inclusive).
- SEE ALSO
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acos, asin, atan, cos, sin, tan
- EXAMPLE
link:src/atan2.c[role=include]- OUTPUT
$ gcc -Wall -lm atan2.c $ ./a.out ATAN2(-10.000000/-1.000000) = -1.670465 ATAN2(-9.000000/-1.000000) = -1.681454 ATAN2(-8.000000/-1.000000) = -1.695151 ATAN2(-7.000000/-1.000000) = -1.712693 ATAN2(-6.000000/-1.000000) = -1.735945 ATAN2(-5.000000/-1.000000) = -1.768192 ATAN2(-4.000000/-1.000000) = -1.815775 ATAN2(-3.000000/-1.000000) = -1.892547 ATAN2(-2.000000/-1.000000) = -2.034444 ATAN2(-1.000000/-1.000000) = -2.356194 ATAN2(0.000000/-1.000000) = 3.141593 ATAN2(1.000000/-1.000000) = 2.356194 ATAN2(2.000000/-1.000000) = 2.034444 ATAN2(3.000000/-1.000000) = 1.892547 ATAN2(4.000000/-1.000000) = 1.815775 ATAN2(5.000000/-1.000000) = 1.768192 ATAN2(6.000000/-1.000000) = 1.735945 ATAN2(7.000000/-1.000000) = 1.712693 ATAN2(8.000000/-1.000000) = 1.695151 ATAN2(9.000000/-1.000000) = 1.681454