Mathigon
Mathigon: Euclidean Geometry: Euclid's Axioms
This lesson focuses on Euclid's Axioms, simple, intuitive statements, that everyone agrees are true. An axiom(or postulate) is a mathematical statement that is regarded as "self-evident" and accepted without proof. A key part of...
Boston University
Fractal Geometry of the Mandelbrot Set Ii
This web site addresses counting and adding in fractal operations, as well as the role of the Fibonacci sequence in fractal geometry.
Wolfram Research
Wolfram Math World: Euclid: The Elements
The classic treatise in geometry written by Euclid is presented in English. It is the textbook used for more than 1,000 years in western Europe.
Oswego City School District
Regents Exam Prep Center: Theorems and Postulates for Geometry
Here is a partial list of theorems, postulates, and properties.
Cut the Knot
Cut the Knot!: The Law of Cosines (Cosine Rule)
This site from Cut The Knot provides an overview of the law of cosines, complete with an explanation of the law and a proof of the law.