A right triangle. This is the proof of the Pythagorean Theorem supposedly written by Pythagoras about 500 BC: The Pythagorean Theorem says that in a right triangle, the sum of the squares of the two right-angle [...]
An eclipse of the moon. You can see the curved shadow of the Earth. Logic tells you the earth is round. Making predictions Once people have seen that something happens [...]
This is a right triangle, because one of the angles is a right angle. A right triangle is any triangle where one of the angles is exactly 90 degrees, or a right angle. You [...]
This is a rectangle. A rectangle is a flat shape, in one plane. It's defined by four points at the four corners. A rectangle has two sides of equal length opposite each other, [...]
Geometry: This is an equilateral trangle. What is geometry? The simplest geometric idea is the point, and then the line, the plane, and the solid. Shapes like circles, squares, rectangles, and triangles are flat, and we can think of [...]
This is an isosceles triangle. Definition of an isosceles triangle Isosceles triangles have at least two sides that are exactly the same length. This forces two of their angles to also be acute angles of exactly [...]
This is an equilateral triangle. What makes a triangle equilateral? Equilateral triangles have all three sides exactly the same length. Because their sides are the same length, the three angles of an equilateral triangle are also [...]
Near where Pythagoras lived: Doric temple at Paestum, Italy Who was Pythagoras? Pythagoras lived in the 500s BC. He was one of the first Greek mathematical thinkers that we know about, after Thales. Who [...]
Greek mathematics: An Egyptian papyrus from about 100 AD which is a piece of one of Euclid's books Greek math: geometry not algebra Because people in ancient Greece had only very clumsy [...]
Diagram for proving the Pythagorean Theorem You can prove the Pythagorean Theorem for yourself, using the proof described on the Pythagorean Theorem page. Just get a square piece of paper, and [...]
