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## Code Examples / Notes » atan2

reubs

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);
}

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