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# atan2

(3.0.5 - 3.0.18 only, PHP 4 >= 4.0.0)

atan2 -- arc tangent of two variables

## Description

``float atan2` (float y, float x)`

This 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 function returns the result in radians, which is between -PI and PI (inclusive).

See also acos() and atan().

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