How to get the position of element transformed with css rotate

Question

I'm having a problem with getting the position of a div after rotate filter is applied to it. I have the position of one end, its height, and the angle by which it is rotated, but after checking what this filter actually does on MDN ("[cos(angle) sin(angle) -sin(angle) cos(angle) 0 0]") I still don't know how to crack it.

Example :

The div I'm interested in is the dashed line. Its styling at that moment was :

left: 80px; top: 12px; height: 69.5122px; width: 2px; -moz-transform: rotate(-1.21366rad);

(top/left describe the position of its beginning.) I'm trying to get the top/left position of its end.

Answer 1

Per your current Question and your requested confirmation of:

var x = termin.top + Math.cos(angle) * div.height; var y = div.left + Math.sin(angle) * div.height; 

The solution can be found in this other SO Answer for a different question, enhanced here:

// return an object with full width/height (including borders), top/bottom coordinates var getPositionData = function(el) {     return $.extend({         width: el.outerWidth(false),         height: el.outerHeight(false)     }, el.offset()); };  // get rotated dimensions    var transformedDimensions = function(el, angle) {     var dimensions = getPositionData(el);     return {         width: dimensions.width + Math.ceil(dimensions.width * Math.cos(angle)),         height: dimensions.height + Math.ceil(dimensions.height * Math.cos(angle))     }; }; 

Here's an interactive jsFiddle that provides real-time updates for getPositionData(); function.
You'll be able to see the top and left values at the end of the CSS3 Rotation process you control.

Reference:   jsFiddle

Status Update: The above jsFiddle works great for 0-90deg and can be approved upon for all angles and different units such as rad, grad, and turn.