src/aria/touch/Pinch.js
function (x1, y1, x2, y2) {
            return Math.atan2(y2 - y1, x2 - x1) * 180 / Math.PI;
        }
function (x1, y1, x2, y2) {
            return Math.atan2(y2 - y1, x2 - x1) * 180 / Math.PI;
        }
function ( x1 , y1 , x2 , y2 ) { return Math . atan2 ( y2 - y1 , x2 - x1 ) * 180 / Math . PI ; }
Returns the angle of the line defined by two points, and the x axes.
@param {Integer} x1 x of the first point
@param {Integer} y1 y of the first point
@param {Integer} x2 x of the second point
@param {Integer} y2 y of the second point
@private
@return {Number} the angle in degrees ]-180; 180]
Returns the angle of the line defined by two points and the x axes .