public static bool get_angle (Event event1, Event event2, out double angle)
Returns the relative angle from
The relative angle is the angle between the X axis and the line through both events' positions. The rotation direction for positive angles is from the positive X axis towards the positive Y axis.
This assumes that both events have X/Y information. If not, this function returns false.
return location for the relative angle between both events
true if the angle could be calculated.