The Pythagoras - The Greek mathematician Pythagoras has high name recognition, not only in the history of mathematics.
The Babylonians - The Babylonians knew the relationship between the length of the diagonal of a square and its side. This was probably the first number that was considered irrational.
A People Who Used The Pythagoras Theorem - As to the claim that the Egyptians knew and used the Pythagorean Theorem in building the great pyramids.
The Teacher Who Collecting Proofs of The Pythagorean Theorem - Elisha Scott Loomis (1852–1940), an eccentric mathematics teacher from Ohio, spent a lifetime collecting all known proofs of the Pythagorean Theorem and writing them up in The Pythagorean Proposition
A 12-Year-Old Einstein ‘Proves’ The Pythagorean Theorem - According to his autobiography, Albert Einstein devised a new ‘proof’ of the Pythagorean Theorem based on the properties of similar triangles.
Pythagorean Theorem in the Special Theory of Relativity - Albert Einstein's Metric equation is simply Pythagoras’ Theorem applied to the three spatial coordinates and equating them to the displacement of a ray of light.
Euclid's Elements - Euclid of Alexandria was a Greek mathematician and is often referred to as the Father of Geometry. Euclid provided two very different proofs of the Pythagorean Theorem.
Book VI, Proposition 31 - In right-angled triangles the figure on the side opposite the right angle equals the sum of the similar and similarly described figures on the sides containing the right angle.
Book I, Proposition 47 - In right-angled triangles the square on the side opposite the right angle equals the sum of the squares on the sides containing the right angle.