Lines of equal length are marked with dashes. In the following diagram, DE is parallel to AC, and AB = CB. a) Find the size of angle \({a}\). Give a reason for your answer. b) Find the size of ...

However, for the lines to be parallel, the distance between the lines always stays the same. Perpendicular lines meet at a right angle. A right angle is a quarter turn, which is 90 degrees (90˚).