Welcome to Theorems and Problems about Circles

Inca Trail to Machu Picchu, the Lost City of the Incas
 

Welcome to Theorems and Problems about circles.

Circles: Table of Content

 

76.

Feuerbach Theorem
One of the most striking theorems in triangle geometry.

75.

Feuerbach Point Facts
 

74.

Feuerbach Theorem, Acute Triangle illustration
 

73.

Feuerbach Theorem, Obtuse Triangle illustration
 

72.

Hippocrates and Squaring the Circle
 

71.

Lunes of Hippocrates 4
 

70.

Lunes of Hippocrates 3
 

69.

Lunes of Hippocrates 2
 

68.

Lunes of Hippocrates 1
 

67.

Pythagoras and Circle Area
 

66.

Brahmagupta's Theorem Cyclic quadrilateral.

65.

Brahmagupta's Corollary Cyclic quadrilateral.

64.

Brahmagupta's Formula  Area of a cyclic quadrilateral.

63.

Mascheroni Construction with compass alone. Midpoint of a segment

62.

Sangaku Proposed Problem 41. "Mickey Mouse."
Three circles, tangents, radii.

61.

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

60.

Lemoine Theorem

59.

Second Ajima-Malfatti Point
Interactive illustration.

58.

First Ajima-Malfatti Point
Animated illustration.

57.

Proposed Problem 39.
Triangle, Incircle, Bisector, Cyclic Quadrilateral and angles.

56.

Proposed Problem 39 Geometry Help.
Facts you should know for the proposed problem 39.

55.

Proposed Problem 38.
Right Triangle, altitude, incircles, incenters, and angles.

54.

Proposed Problem 35.
Incenters and Inradii in Cyclic Quadrilateral.

53.

Sawayama -Thebault's theorem

52.

Proposed Problem 34.
Right triangle, cevian, incircles, tangents and inradius.

51.

Apollonius' Problem for Three Circles Illustration with animation and sound.

 

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Last updated: March 23, 2009