atan2

(PHP 4, PHP 5)

atan2 — 两个参数的反正切

说明

float atan2 ( float $y , float $x )

本函数计算两个变量 x 和 y 的反正切值。和计算 y / x 的反正切相似，只除了两个参数的符号是用来确定结果的象限之外。

本函数的结果为弧度，其值在 -PI 和 PI 之间（包括 -PI 和 PI）。

参见 acos() 和 atan()。

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atan2

Monte Shaffer
09-Jun-2007 02:35


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);

    }

reubs at idsdatanet dot com
24-May-2003 04:01


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. :)

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atan

asinh

Last updated: Mon, 26 Nov 2007