Outline
Geometry Proof Challenges
Table of Contents
Lines and Angles
- Cut-The-Knot-Action (5)!
- Animation 214
- Cut-the-Knot-Action (3)!
- Animation 188
- GoGeometry Action 40!
- Animation 259
- GoGeometry Action 41!
- Animation 260
- GoGeometry Action 58!
- Animation 278
- GoGeometry Action 63!
- GoGeometry Action 65!
- Animation 285
- Concave Quadrilateral Craziness! (GoGeometry Action 80)
- Hexagonal Surprise! (GoGeometry Action 85)
- GoGeometry Action 123!
- GoGeometry Action 143!
- SolveMyMaths Action 2!
- GoGeometry Action 158!
- GoGeometry Action 159!
- GoGeometry Action 168!
- GoGeometry Action 169!
- SolveMyMaths Action 7!
- Regular Polygon Phenomena!
- Regular Nonagon Simplicity (GoGeometry Action 175!)
- More Nonagon Wonders (GoGeometry Action 176!)
Triangles
- Medians & Equal Areas!
- Animation 74
- Animation 90
- Euler Line (Informal Investigation)
- Euler Line Generator
- Morley Action!
- Animation 113
- Napoleon Motion!
- Animation 14
- Hexagonal Napoleon Theorem?
- Animation 172
- Viviani Action! (REVAMPED)
- Equilateral Action (1)!
- Animation 91
- Equilateral Action (2)!
- Animation 94
- Equilateral Action (3)!
- Animation 107
- Equilateral Action (4)!
- Animation 108
- Equilateral Triangle and Rectangle (Area Problem)
- Animation 154
- Equal Triangular Areas in a Regular Pentagon
- Animation 194
- NCTM Calendar Problem (11-2-2016)
- Animation 139
- 9 Point Circle Action
- Animation 34
- 9-Point Circle Action (Part 2)
- Animation 106
- 9-Point Circle Action (Part 3A)
- 9-Point Circle (Informal Investigation)
- Animation 71
- 9-Point Circle Action (Part 3B)
- 9-Point Circle Action (Part 4)
- Animation 53
- 9-Point Circle Action (Part 5)
- Animation 115
- Isosceles Triangle: Surprising Theorem!
- Animation 121
- Cut-The-Knot Action !!!
- More Triangle Action!!!
- Animation 163
- Triangle Median & Circles Action!!!
- Animation 164
- Desargues Action!!!
- Animation 209
- GoGeometry Action 10!
- Animation 219
- GoGeometry Action 14!
- Animation 223
- GoGeometry Action 17!
- Animation 228
- GoGeometry Action 18!
- Animation 229
- Cut-The-Knot-Action 8!
- Animation 230
- GoGeometry Action 20!
- Animation 233
- Cut-The-Knot Action 9!
- Animation 234
- Carnot Action! = GoGeometry Action 27!
- Animation 241
- GoGeometry Action 29!
- Animation 244
- GoGeometry Action 30!
- Animation 245
- Incircle + Excircle = GoGeometry Action 31!
- Animation 246
- GoGeometry Action 32!
- Animation 247
- Cut-The-Knot Action 10!
- Animation 248
- GoGeometry Action 34!
- Animation 250
- Cut-The-Knot-Action 12!
- Animation 251
- GoGeometry Action 35!
- Animation 252
- GoGeometry Action 37!
- Animation 254
- GoGeometry Action 38!
- Animation 255
- GoGeometry Action 39!
- Animation 258
- GoGeometry Action 43!
- Animation 263
- GoGeometry Action 44!
- Animation 264
- GoGeometry Action 51!
- Animation 270
- GoGeometry Action 53!
- Animation 272
- Euler Line Surprise! = GoGeometry Action 54
- Animation 273!
- GoGeometry Action 60!
- Animation 280
- Animation 283
- GoGeometry Action 64!
- Animation 284
- GoGeometry Action 66!
- Animation 286
- GoGeometry Action 68!
- Animation 288
- GoGeometry Action 74!
- GoGeometry Action 75!
- GoGeometry Action 76!
- GoGeometry Action 78!
- GoGeometry Action 82!
- GoGeometry Action 83!
- Cut-the-Knot Action 15!
- Equilateral Triangle + Semicircle = ? (GoGeometry Action 88)
- GoGeometry Action 89!
- GoGeometry Action 90!
- GoGeometry Action 91!
- GoGeometry Action 93!
- GoGeometry Action 97!
- GoGeometry Action 101 !
- GoGeometry Action 103!
- GoGeometry Action 104!
- GoGeometry Action 105!
- GoGeometry Action 106!
- GoGeometry Action 107!
- GoGeometry Action 109!
- SolveMyMaths Action 1!
- GoGeometry Action 110!
- GoGeometry Action 112!
- GoGeometry Action 113!
- GoGeometry Action 115!
- GoGeometry Action 117!
- Blanchet Action = GoGeometry Action 118!
- GoGeometry Action 120!
- GoGeometry Action 121!
- GoGeometry Action 124!
- GoGeometry Action 125!
- Cut-The-Knot Action 18!
- Cut-The-Knot Action 19!
- GoGeometry Action 127!
- Incircle Extension = GoGeometry Action 132!
- Incircle Extension 2 = GoGeometry Action 133!
- GoGeometry Action 134!
- GoGeometry Action 135!
- GoGeometry Action 138!
- GoGeometry Action 147!
- GoGeometry Action 152!
- GoGeometry Action 156!
- GoGeometry Action 160!
- Regular Decagon Magic!
- GoGeometry Action 161!
- GoGeometry Action 162!
- GoGeometry Action 163!
- Equilateral Triangles Problem
- GoGeometry Action 166!
- Feuerbach Action! (GoGeometry Action 167)
- GoGeometry Action 170!
- GoGeometry Action 171!
- GoGeometry Action 174!
- GoGeometry Action 182!
- GoGeometry Action 183!
- GoGeometry Action 184!
- GoGeometry Action 185!
- GoGeometry Action 188!
- GoGeometry Action 189!
- Regular Octagon Phenomenon (GoGeometry Action 190)
Parallelograms
- Finsler-Hadwiger Action!!!
- Animation 110
- Thebault Action!!!
- Animation 83
- Van Aubel Action!!!
- Animation 109
- Square Problem
- 3 Squares Problem
- Animation 120
- Harmonic Mean In an Isosceles Trapezoid
- Square Action! (Proof Problem 1)
- Cut-The-Knot Action (4)!
- Animation 213
- Rhombus Action + Sequel = GoGeometry Action 7!
- Animation 215
- GoGeometry Action 11!
- Animation 220
- GoGeometry Action 12!
- Animation 221
- GoGeometry Action 18!
- Animation 231
- GoGeometry Action 21!
- Animation 235
- GoGeometry Action 22!
- Animation 236
- GoGeometry Action 23!
- Animation 237
- GoGeometry Action 24!
- Animation 238
- GoGeometry Action 36!
- Animation 253
- Cut-the-Knot-Action 13!
- Animation 257
- GoGeometry Action 42!
- Animation 261
- Cut-The-Knot-Action 14!
- Animation 262
- GoGeometry Action 45!
- Animation 265
- GoGeometry Action 46!
- Animation 266
- GoGeometry Action 47!
- Animation 267
- Rhombus Surprise! (GoGeometry Action 57)
- Animation 277
- GoGeometry Action 67!
- Animation 287
- GoGeometry Action 69!
- Square + Rhombus = Constant Surprise! (GoGeometry Action 71)
- GoGeometry Action 73!
- Parallelogram? Why So? (GoGeometry Action 77)
- Square and Quarter Circle Action = GoGeometry Action 81!
- 3 Squares Problem (II)
- GoGeometry Action 94!
- GoGeometry Action 95!
- GoGeometry Action 96!
- GoGeometry Action 98!
- GoGeometry Action 99!
- GoGeometry Action 102 !
- Square + Regular Hexagon Action!
- GoGeometry Action 108!
- GoGeometry Action 114!
- GoGeometry Action 119!
- Cut-The-Knot Action 17!
- GoGeometry Action 126!
- GoGeometry Action 130!
- GoGeometry Action 136!
- GoGeometry Action 139!
- GoGeometry Action 140!
- Parallelogram + 2 Equilateral Triangles: How to Prove?
- GoGeometry Action 153!
- GoGeometry Action 165!
- Shearer Action 1! (Regular Octagon Problem)
- Shearer Action 6!
- GoGeometry Action 181!
- GoGeometry Action 186!
- GoGeometry Action 187!
Geometric Constructions
Circle Theorems
- Butterfly Theorem Action!
- Animation 132
- Not Your Everyday Chord & Tangent Theorem
- Animation 133
- Cut-The-Knot Action (2) !!!
- Animation 152
- Int+Ext Tangent Action!
- Animation 155
- Square, Tangent, and Two Congruent & Tangent Circles
- Animation 153
- GoGeometry Action 1!
- Animation 205
- GoGeometry Action 2!
- Animation 206
- GoGeometry Action 3!
- Animation 207
- GoGeometry Action 4!
- Animation 208
- GoGeometry Action 5!
- Animation 210
- GoGeometry Action 6!
- Animation 212
- GoGeometry Action 8!
- Animation 216
- Cut-The-Knot Action (6)!
- Animation 217
- GoGeometry Action 9!
- Animation 218
- GoGeometry Action 13!
- Animation 222
- GoGeometry Action 15!
- Animation 224
- GoGeometry Action 16!
- Animation 226
- Cut-The-Knot Action 7!
- Animation 227
- GoGeometry Action 19!
- Animation 232
- Thales Action + Sequel = GoGeometry Action 25!
- Animation 239
- GoGeometry Action 26!
- Animation 240
- Carnot Action! = GoGeometry Action 27!
- Animation 241
- Incircle + Excircle = GoGeometry Action 31!
- Animation 246
- Cut-The-Knot Action 10!
- Animation 248
- Cut-The-Knot-Action 11!
- Animation 249
- GoGeometry Action 48!
- Animation 268
- GoGeometry Action 49!
- GoGeometry Action 50!
- Animation 269
- GoGeometry Action 52!
- Animation 271
- 60-Degree Sector Surprise! (GoGeometry Action 55)
- Animation 274
- Neusis Logic Action = GoGeometry Action 56!
- Animation 275
- Animation 276
- GoGeometry Action 59!
- Animation 279
- GoGeometry Action 61!
- Animation 281
- GoGeometry Action 62!
- Animation 282
- GoGeometry Action 70!
- GoGeometry Action 72!
- GoGeometry Action 79!
- Geometric Mean Madness! (GoGeometry Action 84)
- Mickey Mouse Theorem! (Cut-the-Knot Action 16)
- More Geometric Mean Action! (GoGeometry Action 86)
- GoGeometry Action 87!
- GoGeometry Action 92!
- A Stronger Conclusion!
- GoGeometry Action 100!
- GoGeometry Action 116!
- GoGeometry Action 122!
- GoGeometry Action 128!
- GoGeometry Action 129!
- GoGeometry Action 131!
- GoGeometry Action 137!
- GoGeometry Action 142!
- Circle Optimization Challenge!
- SolveMyMaths Action 5!
- GoGeometry Action 148!
- Cyclic Quadrilateral: Quick Warm Up (GoGeometry Action 149!)
- Archimedes Insight = GoGeometry Action 150!
- More Archimedes Insight = GoGeometry Action 151!
- GoGeometry Action 154!
- GoGeometry Action 155!
- Archimedes Insight 3: GoGeometry Action 157!
- GoGeometry Action 164!
- GoGeometry Action 172!
- Shearer Action 4!
- GoGeometry Action 177!
- Shearer Action 5!
- V. Pantaloni Chord Problem
Prove Similarity Theorems
Parabolas
Ellipses and hyperbolas
Other Geometry Resources