The Area of a Disk
The area of a disk is pi times radius squared. You memorized this in middle school. But do you know…
Geometry
Triangle Inequality
The triangle inequality sounds obvious. No side of a triangle can be longer than the other two sides combined. But…
The Poincare Conjecture: The Problem That Made a Mathematician Refuse a Million Dollars
In 1904, Poincare asked: if every loop on a 3D shape can be shrunk to a point, must it be…