Thomsen's Figure
Take any Triangle with Vertices 
, 
, and 
. Pick a point 
on the sideopposite , and draw a line Parallel to 
. Upon reaching the side 
at 
, draw the line Parallelto 
. Continue (left figure). Then 
for any Triangle. If is the Midpoint of , then
(right figure).
References
Madachy, J. S. Madachy's Mathematical Recreations. New York: Dover, pp. 234, 1979.
- Flat Space Theorem
- Flat Surface
- Flattening
- Flemish Knot
- Fletcher Point
- Flexagon
- Flexatube
- Flexible Polyhedron
- Flip Bifurcation
- Floor Function
- Floquet Analysis
- Floquet's Theorem
- Flow
- Flower
- Flower of Life
- Flow Line
- Flowsnake
- Flowsnake Fractal
- Floyd's Algorithm
- Fluent
- Fluxion
- Flype
- Flyping Conjecture
- Focus
- Fold Bifurcation