| December 26, 2004 |
Droz-Farny Circles |
| December 25, 2004 |
Perpendicular Bisectors in an Inscriptible Quadrilateral II |
| December 24, 2004 |
Angle Bisectors and Perpendiculars in a Quadrilateral |
| December 23, 2004 |
Perpendicular Bisectors in an Inscriptible Quadrilateral |
| December 21, 2004 |
Droz-Farny Line Theorem |
| December 19, 2004 |
Reflections of a Point on the Circumcircle |
| December 18, 2004 |
Reflections of a Line Through the Orthocenter |
| December 16, 2004 |
Reflections of the Orthocenter |
| December 12, 2004 |
Intersecting Chords Theorem |
| December 10, 2004 |
Tangent and Secant |
| December 9, 2004 |
Isogonal and Isotomic Conjugalities |
| December 8, 2004 |
Squares Inscribed In a Triangle III |
| December 7, 2004 |
Square Inscribed in a Triangle II |
| December 6, 2004 |
Cevian Triangle |
| November 29, 2004 |
Convex Polygon Is the Intersection of Half Planes |
| November 26, 2004 |
Pedal Polygons |
| November 17, 2004 |
Sierpinski's Gasket and Dihedral Symmetry |
| November 10, 2004 |
Rolle's and Mean Value Theorems |
| November 8, 2004 |
Addition and Subtraction of Functions |
| November 5, 2004 |
The Length of the diagonal of the unit square equals the square root of 2 |
| November 4, 2004 |
Suan Pan in Various Number Systems |
| November 3, 2004 |
Soroban in Various Number Systems |
| November 2, 2004 |
Three Similar Polygons |
| October 31, 2004 |
Color Cycling on the Mandelbrot Set |
| October 22, 2004 |
Venn Diagrams |
| October 14, 2004 |
Distributive Law |
| October 12, 2004 |
Circles On Cevians |
| October 9, 2004 |
Three Similar Triangles II |
| October 8, 2004 |
Two Squares and Another Square and Directly Similar Figures |
| October 6, 2004 |
Three Similar Triangles |
| October 5, 2004 |
Four Circles In a Triangle |
| October 4, 2004 |
Monotone Number Sequences |
| September 28, 2004 |
Stick Broken Into Three Pieces (Cartesian Coordinates) |
| September 23, 2004 |
Proof #44 of the Pythagorean Theorem |
| September 18, 2004 |
Equilateral Triangles On Sides of a Parallelogram |
| September 17, 2004 |
Anticomplementary Triangle Surprise |
| September 15, 2004 |
Three Isosceles Triangles |
| September 14, 2004 |
A Tool for Constructing Orthogonal Latin Squares |
| September 12, 2004 |
Tangents and Diagonals in Cyclic Quadrilateral |
| September 10, 2004 |
Six Circles Theorem (Elkies) |
| September 9, 2004 |
Six Circles Theorem (Evelyn) |
| September 8, 2004 |
Stick Broken Into Three Pieces (Trilinear Coordinates) |
| September 5, 2004 |
Sam Loyd's Son's Dissection |
| September 4, 2004 |
Langman's Paradox |
| September 3, 2004 |
Curry's Paradox |
| August 31, 2004 |
Upgraded Tower of Hanoi |
| August 29, 2004 |
Monge via Desargues II |
| August 28, 2004 |
Radical Axis and Center, an Application |
| August 27, 2004 |
Monge via Desargues |
| August 25, 2004 |
Counting Triangles |
| August 7, 2004 |
Radical Center |
| August 6, 2004 |
Flipping Items Simultaneously II |
| August 5, 2004 |
Flipping Items Simultaneously |
| July 24, 2004 |
Cevian Nest |
| July 19, 2004 |
Wythoff's Nim II |
| July 18, 2004 |
Grundy's Game |
| July 12, 2004 |
Segment Trisection |
| July 5, 2004 |
Upgraded the Farmer and Wife To Catch Rooster and Hen puzzle |
| June 21, 2004 |
Upgraded the Kayles game |
| June 20, 2004 |
Rouse Ball's Fallacy |
| June 18, 2004 |
Four Incident Circles |
| June 17, 2004 |
Proizvolov's Identity |
| June 15, 2004 |
Plainim Misère |
| June 12, 2004 |
Touching Circles |
| June 9, 2004 |
Symmedian and the Tangents |
| June 8, 2004 |
Symmedian and 2 Antiparallels |
| June 7, 2004 |
Symmedian and Antiparallel |
| June 6, 2004 |
Three Tangents Theorem |
| June 5, 2004 |
A Tangent in Concurrency |
| June 1, 2004 |
Chvatal's Art Gallery Theorem |
| May 30, 2004 |
According to the Rules |
| May 18, 2004 |
Scoring Misère |
| May 6, 2004 |
Vecten's Collinearity |
| April 5, 2004 |
Inversion in the Incircle |
| April 2, 2004 |
Carnot's Theorem |
| March 28, 2004 |
Viviani's Theorem |
| March 27, 2004 |
Nobbs' Points, Gergonne Line |
| March 25, 2004 |
Tromino Puzzle |
| March 24, 2004 |
Tiling a Triangulated Hexagon |
| March 22, 2004 |
Polygons Formed by Perpendicular Bisectors |
| March 21, 2004 |
Quadrilaterals Formed by Perpendicular Bisectors |
| March 18, 2004 |
Equilateral Triangles on Sides of a Quadrilateral |
| March 14, 2004 |
Four Pegs That Form a Square |
| March 7, 2004 |
The Parabola |
| February 26, 2004 |
Updated the Twelve Matchsticks Area Puzzle |
| February 25, 2004 |
Updated the page on solving xx3 = 3 |
| February 14, 2004 |
Solution to the BiColor Tower of Hanoi puzzle, by N. Bowler |
| February 2, 2004 |
Collinearity in Bicentric Quadrilaterals |
| February 1, 2004 |
Projective Collinearity in a Quadrilateral |
| January 31, 2004 |
Easy Construction of Bicentric Quadrilateral II |
| January 30, 2004 |
Easy Construction of Bicentric Quadrilateral |
| January 29, 2004 |
Squares on Sides of a Quadrilateral |
| January 27, 2004 |
Three Incircles in a Triangle |
| January 25, 2004 |
Two Quadrilaterals |
| January 24, 2004 |
Diagonals in a Cyclic Quadrilateral |
| January 21, 2004 |
Ceva in Circumscribed Quadrilateral |
| January 10, 2004 |
Zaslavsky's theorem |
| January 4, 2004 |
Erro Ergo Disco |
