Online Geometry, See also:




Ceva's Theorem.
Concurrency.
Interactive proof with animation.
Puzzle of
the Ceva's Theorem: 48 classic piece. 

Pascal's Mystic Hexagram Theorem Proof 

Blanchet Theorem


Nagel Point
Theorem. Proof.


Nagel Point
Theorem  Flowchart Proof .


Gergonne Point Theorem.
Concurrency.
Interactive proof with animation.
Key concept: Ceva's
Theorem.


Triangle with the bisectors of the
exterior angles. Collinearity.Key concept:
Menelaus Theorem.


Monge &
d'Alembert Three Circles Theorem I with Dynamic Geometry 

Monge & d'Alembert Three Circles
Theorem II with Dynamic Geometry 

Newton's
Theorem: Newton's Line. Circumscribed quadrilateral, midpoints of
diagonals, center of the circle inscribed.
Puzzle of the Newton's Theorem:
50 pieces of circles. 

Pentagons
& Pentagrams. I found, exploring with dynamic geometry software, new
facts about pentagons and pentagrams. Key concept: Menelaus Theorem.
See also:
Pentagons & Pentagrams  Puzzle:
96 triangles. 

Van Aubel's Theorem II: Triangle and Cevians.


Eyeball Theorem:
Animated Angle to Geometry Study.


Geometry Problem 659.
Parallelogram, Parallel Lines, Collinear Points. 

