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Arc tangent of two variables
(PHP 4, PHP 5)
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
Code Examples / Notes » atan2reubs
Just a note: PHP's atan2 function receives parameters in (y,x) and Excel receives it in (x,y) format. Just in case you are porting formulas across. :) monte shaffer
Here is a function that will return a new point [Rotate around non-origin pivot point] (x,y) is current point (cx,cy) is pivot point to rotate =a= is angle in degrees $_rotation = 1; # -1 = counter, 1 = clockwise $_precision = 2; # two decimal places function returnRotatedPoint($x,$y,$cx,$cy,$a) { # http://mathforum.org/library/drmath/view/63184.html global $_rotation; # -1 = counter, 1 = clockwise global $_precision; # two decimal places // radius using distance formula $r = sqrt(pow(($x-$cx),2)+pow(($y-$cy),2)); // initial angle in relation to center $iA = $_rotation * rad2deg(atan2(($y-$cy),($x-$cx))); $nx = number_format($r * cos(deg2rad($_rotation * $a + $iA)),$_precision); $ny = number_format($r * sin(deg2rad($_rotation * $a + $iA)),$_precision); return array("x"=>$cx+$nx,"y"=>$cy+$ny); } |
