Atan2

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atan2 is a two-parameter function for computing the arctangent in the C programming language, C++, Java, C#, Fortran and many other modern programming langauges. The Linux Programmer's Manual [link] says:

"The atan2 C++ function calculates the arctangent of the two variables x and y. It is similar to calculating the arctangent of y/x, except that the signs of both arguments are used to determine the quadrant of the result."

This is the preferred form [link] for correctly finding the sign of the result in all quadrants. See also inverse trigonometric function.

More specifically, the function atan2(y,x) is defined as the arctangent of y/x with a range from (-π,π], determined by:

if x = y = 0, then the result is indefinite,
if x > 0 and y = 0, then atan2 = 0,
if x < 0 and y = 0, then atan2 = π, else
if y < 0, then −π < atan2 < 0,
if y > 0, then 0 < atan2 < π.

This function is used to find the direction from one point to another in 2-dimension Euclidean space.

External links

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