I started teaching in 1977, and across my nearly 50 years, I noticed that students were always interested in the history of ...

Parallel lines are indicated by arrows going in the same direction. If there is more than one set of parallel lines in a diagram, different numbers of arrows are used. The three lines in this ...

Parallel lines are lines that never cross each other - they keep the same distance apart from each other. When two lines intersect, the opposite (X) angles are equal. On parallel lines ...