Khan Academy on a Stick
Right triangles
Triangles are not always right (although they are never wrong), but when they are it opens up an exciting world of possibilities. Not only are right triangles cool in their own right (pun intended), they are the basis of very important ideas in analytic geometry (the distance between two points in space) and trigonometry.

Pythagorean Theorem
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Pythagorean Theorem

The Pythagorean theorem intro
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Introduction to the Pythagorean Theorem

Pythagorean Theorem 1
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Pythagorean Theorem 1

Pythagorean Theorem 2
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Pythagorean Theorem 2

Pythagorean Theorem 3
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Pythagorean Theorem 3

Introduction to the Pythagorean Theorem
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Right triangles and the Pythagorean Theorem

Pythagorean Theorem II
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More Pythagorean Theorem examples. Introduction to 454590 triangles.
Pythagorean theorem
Named after the Greek philosopher who lived nearly 2600 years ago, the Pythagorean theorem is as good as math theorems get (Pythagoras also started a religious movement). It's simple. It's beautiful. It's powerful. In this tutorial, we will cover what it is and how it can be used. We have another tutorial that gives you as many proofs of it as you might need. In thi

Garfield's proof of the Pythagorean Theorem
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James Garfield's proof of the Pythagorean Theorem.

Bhaskara's proof of Pythagorean Theorem
An elegant visual proof of the Pythagorean Theorem developed by the 12th century Indian mathematician Bhaskara.

Pythagorean Theorem Proof Using Similarity
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Proof of the Pythagorean Theorem using similarity

Another Pythagorean Theorem Proof
Visually proving the Pythagorean Theorem
Pythagorean theorem proofs
The Pythagorean theorem is one of the most famous ideas in all of mathematics. This tutorial proves it. Then proves it again... and again... and again. More than just satisfying any skepticism of whether the Pythagorean theorem is really true (only one proof would be sufficient for that), it will hopefully open your mind to new and beautiful ways to prove something very powerful.

306090 Triangle Side Ratios Proof
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Proving the ratios between the sides of a 306090 triangle

454590 Triangle Side Ratios
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Showing the ratios of the sides of a 454590 triangle are 1:1:sqrt(2)

306090 Triangle Example Problem
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Using what we know about 30600 triangles to solve what at first seems to be a challenging problem

Area of a Regular Hexagon
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Using what we know about triangles to find the area of a regular hexagon

454590 Triangles
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Introduction to 454590 Triangles

Intro to 306090 Triangles
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A few more 454590 examples and an introduction to 306090 triangles.

306090 Triangles II
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More examples using 306090 triangles.
Special right triangles
We hate to pick favorites, but there really are certain right triangles that are more special than others. In this tutorial, we pick them out, show why they're special, and prove it! These include 306090 and 454590 triangles (the numbers refer to the measure of the angles in the triangle).