What is the Pythagorean theorem and why is it true?
Triangle's Tile Promise
What is the Pythagorean theorem and why is it true?
Picture a right triangle — a triangle with one perfect square corner, like the corner of this page. It has three sides. There's an old, famous rule about those three sides, and it has been quietly true for thousands of years. People call it the Pythagorean theorem, and once you see why it works, you can't un-see it.
Let's name the sides. The two short sides that meet at the square corner are the legs. The long slanted side across from that corner — the longest one — is the hypotenuse, which is just a fancy word for "the slanty long side." That's all the vocabulary we'll need.
