See also:




1. 

Ceva's Theorem.
Concurrency.
Interactive proof with animation. Key concept:
Menelaus Theorem.
Puzzle of
the Ceva's Theorem: 48 classic piece. 
2. 

Pascal's Mystic Hexagram Theorem Proof 
3. 

Blanchet Theorem

4. 

Nagel Point
Theorem. Proof.

5. 

Nagel Point
Theorem  Flowchart Proof .

6. 

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

7. 

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

8. 

Monge &
d'Alembert Three Circles Theorem I with Dynamic Geometry 
9. 

Monge & d'Alembert Three Circles
Theorem II with Dynamic Geometry 
10. 

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. 
11. 

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. 
12. 

Eyeball Theorem:
Animated Angle to Geometry Study.

13. 

Seven Circles Theorem

14. 

Equal Incircles Theorem 
15. 

Archimedes' Book
of Lemmas

16. 

Butterfly Theorem 
17. 

Triangle Centers

18. 

Euler and his beautiful and
extraordinary formula 
19. 

Semiperimeter and incircle 
20. 

Semiperimeter and excircles of a triangle 
21. 

Semiperimeter, incircle and excircles of a triangle 
22. 

Miquel's
Pentagram with Dynamic Geometry 
23. 

Miquel's Pentagram Theorem. Proof 
24. 

Johnson's Theorem 
25. 

Simson Line 
26. 

Angle between two
Simson Lines 
27. 

Sangaku Problem 
28. 

The
Bevan Point 
29. 

Clifford's Circle Chain
Theorems 
30. 

Kurschak's Tile and Theorem 
31. 

Animated Angle to Geometry Study 
32. 

Proposed Problem 28
Right
Triangle, altitude, incircles and inradius. 
33. 

Steiner Point



