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How round is your circle?

Dudeney's dissection Falling apart.
  1. The Pythagorean Theorem
  2. Dudeney's dissection
  3. Duijvestijn's dissection
  4. Problems
Watt's linkage How to draw an approximately straight line.
  1. James Watt's linkage
  2. Chebyshev's linkage
  3. Chebyshev's linkage - alternative form
  4. Roberts' linkage
Peaucellier's linkage How to draw an exact straight line.
  1. Peaucellier's linkage
  2. Inverse in a circle
  3. Hart's linkage
  4. Hart's A-frame
  5. Sarrus's linkage
A Pantograph Other linkages.
  1. The pantograph
  2. Parallel motion
  3. Four bar variations
  4. Four bar variations 2
  5. The Triple Generation Theorem
Chebyshev's paradoxical mechanism Chebyshev's paradoxical mechanism.
Reuleaux's rotor How round is your circle?
  1. Reuleaux's rotor
  2. Circular arc rotors
  3. Even numbers of arcs
  4. A general triangle
  5. Half a convex shape
Solids of constant width Solids of constant width
  1. Solids of revolution
Drilling a square hole Applications of shapes of constant width.
  1. Coin design
  2. Cams design
  3. Drilling a square hole (1)
  4. Drilling a square hole (2)
  5. The rotary engine car
Stacking dominoes All a matter of balancing dominoes.
  1. Stacking dominoes
  2. Self supporting spiral staircases
  3. Self-righting stacks
The uni-stable polyhedron Amazing polyhedra.
  1. The two-tip tetrahedron
  2. The uni-stable polyhedron
Rolling discs Rolling discs.
  1. Rolling discs
  2. Rolling ellipses
  3. Rolling pears
Measuring area with a bent coat hanger Area and a bent coat hanger.
  1. A hatchet planimeter
  2. The Amsler planimeter