The golden ratio

An introduction to one of the most amazing ideas/numbers in mathematics

Language and notation of the circle

Formal definition of a circle. Tangent and secant lines. Diameters and radii. major and minor arcs

Lines, line segments, and rays

Difference between lines, line segments, and rays

Euclid as the father of geometry

Euclid and his Elements (and how much Abraham Lincoln liked them)