A clean-cut and tidy explanation of perpendicular and parallel, along with a nice little app that lets you make and un-make parallel and perpendicular pairs. Thank goodness they aren't train tracks or you'd have a serious pile-up on your hands.
A short and colorful lesson on parallel lines and transversals. Pay attention to all those special angle pairs that make a transversal so useful because we don't want to repeat ourselves.
A really good summary of the fifth of Euclid's postulates, the Parallel Postulate. It includes a description of attempts to prove the fifth postulate from the other four. It also has a list of true statements that are similar to the fifth postulate and quite useful in future proofs. (Hint, hint.)
What do Euclid and Steven Spielberg have in common? They're both famous, powerful, and masters of their craft, with works that will influence generations to come. What don't they have in common? Pretty much everything else.
Euclid wasn't just an influential mathematician and brilliant thinker. He was an artist, as well. Don't believe us? Check out these insane works of art based on different aspects of Euclidean geometry. No flash photography, please.
This interactive website allows you to build your own proofs by selecting from a pool of statements and reasons. Prove that angles are congruent, that lines are parallel, and that you're a geometry whiz.
A Jeopardy-style game about the important angles relationships formed by parallel lines and a transversal. These relationships last longer than those on the Newlywed Game! Don't forget to phrase your answer in the form of a question.
You've seen enough pictures of parallel lines and transversals. It's about time you saw them in action. Here's our take on parallel lines and transversals, motion picture style.
Guns 'n' Roses should seriously reconsider doing geometry-themed rock songs. They'd build a younger audience and make a fortune doing it. What a comeback that would be.
Mathematicians aren't just logical thinkers. Euclid was creative and artistic as well as brilliant. Of course, some mathematicians prefer congruence to color and proofs to pastels. We don't judge.