Pythagorean theorem - What is it?

Pythagorean theorem is super important for math. You will probably learn about it for the first time in Algebra, but you will literally use it in Algebra, Geometry, Trigonometry, Precalculus, Calculus, and beyond! That’s because the Pythagorean theorem is a tool you’ll use all the time when you’re dealing with triangles, and you will always be dealing with triangles, no matter what math class you’re taking.

Pythagorean key point

In this video you'll learn:

0:23 // What is Pythagorean theorem?
1:21 // What does the Pythagorean theorem state?
2:26 // Does the Pythagorean theorem work for all right triangles?
2:54 // What is the converse of the Pythagorean theorem?
4:11 // Does Pythagorean theorem work for acute or obtuse triangles?
6:45 // Who invented Pythagorean theorem? When was Pythagorean theorem developed?
7:06 // Why is the Pythagorean theorem true? Why does Pythagorean theorem work? (proof of the Pythagorean theorem)
12:18 // How is Pythagorean theorem used in real life? Why learn Pythagorean theorem? (a real world example)
18:30 // What are Pythagorean triples?
22:13 // How do you find Pythagorean triples? 

Pythagorean theorem is of course a^2+b^2=c^2, but it’s so much deeper than just that simple math theorem. In this video we’ll be talking about what the Pythagorean theorem states, and also about the converse of the Pythagorean theorem. The Pythagorean theorem converse is just like looking at the theorem with the reverse logic.

The Pythagorean theorem is credited to a Greek mathematician and philosopher named Pythagoras. While he gets credit for proving it, we know that the Babylonians were using it almost 1500 years earlier!

The theorem is simply a relationship between the side lengths of a right triangle. It says that the square of the hypotenuse is equal to the sum of the the squares of the other two legs of the triangle. It’s also pretty cool that this relationship then gives us an easy way to know if a triangle is obtuse or acute.

In this week’s video, we’re talking more about the Pythagorean theorem, including when it’s used in real life, how to find sets of Pythagorean triples, and we’ll even be walking through an actual proof that shows why the theorem is true. It’s the proof that Pythagoras himself used when he proved this theorem.


Want to learn more about Geometry? I have a step-by-step course for that. 😃

Krista King