Video narration
If you have a right triangle—one angle is exactly 90 degrees—the Pythagorean theorem tells you how the side lengths relate. Label the two shorter sides that make the right angle as a and b. The side opposite the right angle is the hypotenuse, labeled c—and it’s always the longest side. The theorem says: a squared plus b squared equals c squared. In symbols: a² + b² = c². “Squared” just means multiply a number by itself. Here’s a quick example. Suppose a is 3 and b is 4. Then a² is 9 and b² is 16. Add them: 9 + 16 = 25. So c² is 25, and c is 5. This is useful anytime you need a missing distance in a right-angled corner—like checking a diagonal across a rectangle. Just remember: it works only for right triangles.