Its a simple question which have a simple answer.. The answer is that :- When you draw a straight line on a paper you will find that the line is straight and when you measure it by you protector or D you will find that the line is 180° which means this line goes straight and long... And when you draw a line at the same angle and between below to it by giving space from the previous line you draw. The second point was that:- As you know about perpendicular bisector. It is also done by it. When you draw parallel line then do perpendicular bisector (roughly) on it you will find 90° on both side of the line so that means 90°+90°=180° which means it will never interest each other at any condition...