Right Triangle Similarity Theorems: "Geometric Mean"
There are three theorems about right triangles which have been cut in half with the "altitude to the hypotenuse". These geometric mean theorems are super-confusing, so I explain how to make sense of it by always setting up a proportion so you don't have to memorize the crazy equations.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)