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