Congruent Triangles--SSS, SAS, AAS, ASA, H-L

Everything You Need To Know About Congruent Triangles

Okay, not everything. More like the basics, the nuts and bolts, that form the foundation of all the theorems to come: what does congruent mean, what are corresponding parts, how am I supposed to draw those little congruency mark hashtag things on sides and angles, etc.

Tips & Tricks For Congruent Triangle Proofs

This video gives you a couple of the common tricks that seem to keep popping up in proofs again and again, to jog your memory when you're having trouble with a proof. The biggies: the reflexive property of congruence, and vertical angles.


This video is long because it introduces and explains all of the three-letter triangle theorems. The only question this video doesn't answer: why is geometry so obsessed with congruent triangles. Je ne sais quoi.

Why SSA (or ASS) Doesn't Work

This video is short, but it's good for a few laughs (at least from me), and more importantly it answers a question that every student should know because your teacher will expect you to know it. Hint: the ambiguous case.

Triangle Proof How-To

The thing that makes triangle proofs so hard is that there are two levels: somehow you're supposed to learn to "plan" them while simultaneously dotting every i, crossing every t, and worrying about ever little theorem along the way. So in this video we skip the minutia and just talk about the plan for each proof. Then in the next video we'll do the step-by-step part.

Full Proof Examples--SSS, SAS, ASA, AAS, SSA, H-L

To keep things simple, in the previous video we "planned" a bunch of proofs. In this video we follow through on those plans, working out each proof in excruciating detail. Good times.