Chronology of Updates

Note: I have placed chronology of updates for 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 and 2005 into separate files. Starting with 1997, the most recent entries appear topmost. Besides providing an insight into this site's evolution, chronology of updates may be used for word searches.

December 30 Line IO in Bicentric Quadrilaterals
December 29 Equal Angles in Two Circles II
December 25 Hippocrates' Squaring of Lunes
December 15 Quadrature: A Child's Play
December 13 Hippocrates' Squaring of a Lune
December 11 Squaring a Rectangle
December 10 Shearing a Polygon into a Triangle of Equal Area
November 24 Proof 72 of the Pythagorean Theorem
November 22 Pythagorean Theorem: Subtle Dangers of Visual Proof
November 20 Proof 71 of the Pythagorean Theorem
November 19 Cherchez le quadrilatère cyclique II
November 18 Altitudes and the Power of a Point
November 17 Use of Homogeneous Coordinates for Geometrical Calculations, by R. F. Housholder
November 15 Proof 70 of the Pythagorean Theorem
November 9 Orthodiagonal and Cyclic Quadrilaterals
November 8 Circumcenter on Angle Bisector
November 7 Projections on Internal and External Angle Bisectors
November 6 Dissection of Cyclic Quadrilateral
November 5 Orthocentric System From Rectangle
November 3 In the Wasan Spirit
November 2 Equilateral Triangles On Sides of a Parallelogram II
November 1 What Is Angle?
October 27 An Arithmetic Magic Trick
October 26 Finding Circle Center By Ruler Alone
October 26 Cherchez le quadrilatère cyclique
October 25 Equal Angles in Two Circles
October 24 Tangents, Perpendiculars and Geometric Mean
October 22 Why 17?
October 19 Angle: An Illustrated Classification
October 17 A Circle Related to Incenter and Circumcenter
October 16 Ramsey's Theorem
October 15 Property of the Line IO: a proof from the Book
October 10 Inscriptible Quadrilateral: An Illustration
October 10 When A Quadrilateral Is Inscriptible?
October 9 Egyptian Triangle By Paper Folding
October 9 A Problem on an Icy Cone
October 8 Common Chord and a Tangent
October 7 Sangaku and The Egyptian Triangle
October 5 Orthocenters of Two Triangles Sharing Circumcenter and Base
October 3 Combinatorial Proofs
October 1 Dividing Evenly a Quadrilateral II
September 29 Lucas' Theorem
September 28 Area of the Union of Two Squares
September 27 Dividing Evenly a Quadrilateral
September 26 Golden Ratio in Geometry
September 25 Classification of Quadrilaterals
September 24 Parallel Lines in a Quadrilateral
September 23 Impossible Frame
September 22 Triangle Classification
September 21 What Is Proof?
September 18 The SSA
September 17 The SSS
September 16 Expanded the page on Irrationality of sqrt(2) with introduction and two more proofs
September 15 Geometric Meaning of the Geometric Mean
September 14 Geometric Mean Sangaku
September 11 Morley's Theorem, G. Zsolt Kiss' proof
September 10 Circle Concurrency and Spiral Similarity
September 9 Two Quadruplets of Tangent Circles
September 8 Review of Kiselev's Geometry
September 6 Two Circumcircles And Two Pairs of Parallels
September 4 Pythagoras' Theorem Solely By Sliding
August 22 Orthogonality in Isosceles Triangles
August 21 Foot of Altitude and Minimum Distance
August 20 An inequality: 1 + 2-2 + 3-2 + 4-2 + ... + n-2 < 2.
August 19 Ian McGee's Observation
August 18 A Median in Touching Circles
August 16 Midpoints from Gergonne Triangle
August 15 Five Incircles in a Square
August 14 A Sangaku: Two Unrelated Circles
August 12 Chords, Concurrency and Orthic Triangle
August 10 Van Schooten's and Pompeiu's Theorems
August 9 Harmonic Ratio in Complex Domain
August 6 A Sangaku Follow-Up on an Archimedes' Lemma
August 5 A Property of the Line IO: A Bundled Statement and Proof
August 4 A Property of the Line IO
August 3 Three Parallels in a Triangle
August 1 Angle Bisector in Touching Circles
July 31 Discovery of Duane DeTemple
July 30 Two Circumcircles in Triangle
July 27 Right Isosceles Triangles on Sides of a Quadrilateral
July 26 Rotations in Disguise
July 25 Toothpick Construction of a Square
July 22 Fagnano's Problem, Izvolsky's Solution
July 21 Antiparallel
July 21 Nagel's Theorem
July 20 Two Circles on a Side of a Triangle
July 18 Shuttle Puzzle Practice
July 16 Permutations as a Product of Transpositions
July 14 Radius and Construction of a Mixtilinear Circle
July 13 Tromino as a Rep-tile
July 12 Mixtilinear Circles and Concurrence
July 7 Secant, Tangents and Orthogonality
July 6 60° Breeds 90°
July 5 Triangle Areas in a Parallelogram II
June 26 Triangle Areas in a Parallelogram
June 25 Parallelogram and Similar Triangles
June 22 Joachimsthal's Notations
June 21 Urquhart's Theorem
June 21 Reviewed the outstanding The 15 Puzzle
June 20 Kürschak's Tile and Theorem
June 18 Started the Book Reviews section
June 17 MathPro Logo
June 16 Stones in Cups
June 14 Product of permutations
June 13 Recombining Permutations
June 11 Shearing and Translation in Pythagorean Pants
June 10 Pythagoras' Theorem By Sheer Shearing
June 9 Proof 69 of the Pythagorean theorem
June 7 Integer roots of integers are irrational by S. Brodie
June 6 Coloring a Graph
June 5 Parallelogram Law: A PWW
June 5 Parallelogram Law: A Tessellation
June 3 The Law of Cosines: An Unfolded Variant
June 2 The Law of Cosines: a proof without words
May 14 Proof 68 of the Pythagorean theorem
May 14 Parallelogram Law
May 13 Proof 67 of the Pythagorean theorem
May 12 Secant Angles II
May 11 Broken Chord Theorem: S. Anderson's proof
May 10 The Cleavance Center
May 10 The Cleaver
May 9 Broken Chord Theorem by Paper Folding
May 8 Broken Chord Theorem: Patruno's proof
May 7 Broken Chord Theorem
May 6 Angle Subtended by a Diameter
April 29 Graph of a Polynomial Defined by Its Roots
April 28 Graph of a Polynomial
April 27 The ass and the mule
April 26 Midpoints of the Lines Joining In- and Excenters
April 25 Pedoe's Theorem
April 24 Proof 14 of the Butterfly theorem
April 24 ISBN Encoding
April 23 Barcode and EAN-13 Encodings
April 22 Barcode Magic
April 21 Universal Product Code
April 12 Construction of the Angle Bisector
April 11 Existence of the Circumcenter
April 10 Perpendicular Bisector
April 7 Three Touching Circles
April 6 Two Touching Circles
April 3 Proofs 65 and 66 of the Pythagorean theorem
March 29 Pythagoras' Theorem By Similarity
March 29 Proof #4 of the Eyeball Theorem
March 29 Proof #8 of Irrationality of sqrt(2)
March 28 Equidecomposition of a Triangle and a Rectangle II
March 27 Square in a Right Triangle and its fill-it-in outline solution
March 23 Billy is twice as old as Sally and other Outline Mathematics
March 21 Areas and Centroid in a Triangle
March 18 Proof 64 of the Pythagorean theorem
March 18 Proof 63 of the Pythagorean theorem
March 17 Symmedian in a Right Triangle
March 16 Proof 62 of the Pythagorean theorem
March 16 Pennies in Boxes
March 11 Mirror on the Wall
March 10 Math Telepathy
March 9 Rhind Papyrus
March 8 Peasant Multiplication
March 3 Proofs 59, 60, 61 of the Pythagorean theorem
February 28 Started a page on False Proofs of the Pythagorean Theorem
February 28 Proofs 56, 57, 58 of the Pythagorean theorem
February 27 A Problem In an Isosceles Right Triangle
February 26 Equal Areas In Parallelogram à la Pythagoras
February 25 Two Homotheties in a Parallelogram
February 22 3-Color Tower of Hanoi (Algorithm)
February 21 Another Sticky Problem II
February 19 Four Turtles (or Bugs, or Dogs, etc.)
February 17 Bottles in a Wine Rack: Proofs and Generalizations
February 15 Angles in Triangle Add to 180°
February 15 Rendezvous
February 12 Two Symmetric Triangles Are Directly Equidecomposable IV
February 9 Solution to the Four Travelers Problem by Rob Fatland
February 8 Two Symmetric Triangles Are Directly Equidecomposable III
February 7 Two Symmetric Triangles Are Directly Equidecomposable II
February 7 Two Symmetric Triangles Are Directly Equidecomposable
February 6 Angles in Triangle Add to 180°
February 4 Distance From a Point to a Straight Line
February 1 Tangent Circles and an Isosceles Triangle, a Solution
January 31 Radius of a Circle by Paper Folding
January 31 Bottema Shatters Japan's Seclusion
January 30 Tangent Circles and an Isosceles Triangle
January 29 Pythagoras and Vecten Break Japan's Isolation
January 26 Evolution of a Solution
January 25 Triangles, Squares and Areas from Temple Geometry
January 24 Universal Coloring
January 23 No Equilateral Triangles, Please
January 22 Triangle Sliding on Two Straight Lines
January 21 Bottles in a Slanted Rack
January 18 First Geometric Interpretation of Complex Numbers
January 12 Around the Incircle in a Polygon
January 11 Crossed-Lines Construction of Shapes of Constant Width
January 9 Around the Incircle
January 8 Algebraic Structure of Complex Numbers
January 4 Three Concurrent Circles
January 3 Circles And Parallels
January 3 Proof #13 of the Butterfly Theorem
January 3 Carpets in a Quadrilateral
January 2 Two Circles and a Limit

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