  # Online Geometry: Classical Theorems of Euclidean Geometry

## Classical Theorems - Page 1  The significance of the Pythagorean theorem by Jacob Bronowski.
Pythagorean Theorem, 47th Proposition of Euclid's Book I.

Carnot's Theorem. Geometry Problem 889
Carnot's Theorem in an acute triangle, Circumcenter, Circumradius, Inradius. GeoGebra, HTML5 Animation for Tablets. Ceva's Theorem. Concurrency. Interactive proof with animation. Key concept: Menelaus Theorem.

Menelaus' Theorem. Interactive proof with animation and key concepts..

van Aubel's Theorem. Quadrilateral with Squares. Proof with animation.

van Aubel's Theorem. Quadrilateral with Squares. Proof with animation for Tablets, iPad, Nexus, Galaxy.

Heron's Formula.
Key facts and
a purely geometric step-by-step proof.

Euclid's Elements Book I, 23 Definitions. One-page visual illustration.
Euclid's Elements Book. Index

Euclid's Elements, Book XIII, Proposition 10 One page visual illustration.

Clifford's Circle Chain Theorems. This is a step by step presentation of the first theorem. Clifford discovered, in the ordinary Euclidean plane, a "sequence or chain of theorems" of increasing complexity, each building on the last in a natural progression.

Nine-Point Center, Nine-Point Circle, Euler Line.
Interactive illustration.

Soddy Circles and Descartes Theorem.
Three tangent circles, Inscribed and Circumscribed Circles, Radii.

Euler's Problem, Problem 155. Distance between the Incenter to the Circumcenter.

Brahmagupta's Formula  Area of a cyclic quadrilateral.

Brahmagupta's Theorem Cyclic quadrilateral.

Platonic Solids, Interactive animation.
HTML5 Animation for iPad and Nexus
Flash Animation.

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Last updated: Mar 11, 2018  