History of mathematical notation back to any school or period before that of the Ionian Greeks, but the subsequent history may be divided into periods, the distinctions between which are tolerably well marked. Greek mathematics, which originated with the study of geometry, tended from its commencement to be deductive and scientific. Since the fourth century AD, Pythagoras has commonly been given credit for discovering the Pythagorean theorem, a theorem in geometry that states that in a right-angled triangle the area of the square on the hypotenuse (the side opposite the right angle) is equal to the sum of the areas of the squares of
Pythagorean theorem used as a triangle "C" on its hypotenuse, and two similar right triangles ("A" and "B" ) constructed on the other two sides, formed by dividing the central triangle by its altitude. The sum of the areas of the two smaller triangles therefore is that of the third, thus "A" + "B" = "C" and reversing the above logic leads to the Pythagorean theorem a + b = c. ("See also Einstein's proof by dissection without rearrangement") The Pythagorean theorem is a special case of the more general theorem relating the lengths of sides in any triangle, the law of