Here's part two of our intro to the Pythagorean Theorem where we move on to introducing the actual formula of a2 + b2 = c2 to find the sides of a right triangle. The fact that they proved it for themselves first will help them to remember it in the future. It won't be just another formula void of meaning to be memorized for a test.
Using Cuisenaire Rods or other similar manipulatives is an excellent way to introduce complex math concepts to children. They can see and touch math instead of just hearing and writing abstract symbols.