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Pythagorean Theorem Proofs

Proofs of the Pythagorean theorem, a selection of answers from the Dr. Math archives.

The Pythagorean Theorem - Dr. Math FAQ

What is the Pythagorean theorem? When would I use it?

From the archives:

How Many Proofs of the Pythagorean Theorem?

Do you know the exact number of proofs of the Pythagorean Theorem in existence?

The Pythagorean Theorem

Could you please explain the Pythagorean Theorem?

Pythagorean Proof Based on the Principles of Scaling

I've decided to do a project with some connections to the Pythagorean theorem, but the project requires innovative ideas.

First Math Teacher, Pythagorean Theorem

Who was the first math teacher? How did Pythagoreas come up with a^2 + b^2 = c^2?

Proving the Pythagorean Theorem: A Traditional and a Modern Approach

Can you please explain how I can prove the Pythagorean theorem?

Garfield's Pythagorean Theorem Proof

Which President of the United States wrote a proof of the Pythagorean Theorem? On what did he base his proof?

Pythagorean Theorem Proof (Thabit ibn Qurra)

Proving a series of congruent triangles.

Pythagorean Theorem Proof by Brodie Explained

Could you give me a step-by-step explanation of Dr. Scott Brodie's proof of the Pythagorean theorem given at the Cut-the-Knot website?

Pythagorean Theorem - Euclid's Proof

A detailed explanation of a specific proof.

Pythagorean Theorem Proof: Four Right Triangles

I don't understand the Pythagorean Theorem.

Proving the Pythagorean Theorem using Congruent Squares

A friend of mine is irked because of constant use of the Pythagorean theorem, which he has not seen proven.

The Pythagorean Theorem: A Modern Proof

I know that the Pythagorean Theorem works and I can show how it works, but why does it work?

Proof of Pythagorean Theorem: Pythagoras' Reasoning

I would like to know how Pythagoras reasoned his theorem.

Pythagorean Theorem and non-Right Triangles

Why doesn't the Pythagorean theorem work for triangles other than right triangles?

Derivations of Heron's Formula

How is Heron's formula (Hero's formula) derived?