getDistance = function(p1, p2, props) {
		if(!props) {
			props = ['x', 'y'];
		}
		var x = p2[props[0]] - p1[props[0]];
		var y = p2[props[1]] - p1[props[1]];
		return sqrt((x * x) + (y * y));
	}
angle
@param {type} p1
@param {type} p2
@returns {Number}