Compass Constructions Made Easy
A step-by-step guide to compass constructions that go wrong: a slipping circle (just trace a mug), a lopsided perpendicular bisector, an angle bisector lost in arcs, a 17-gon you pretend you drew, a Venn diagram, and a Cantor set.
Transcript
[1] Draw a circle: "1. place compass on page" "2. rotate" "3. oh no, it's slipping" "4. ugh" "5. trace a mug or something" [photo of a mug and a Sharpie]
[6] Perpendicular bisector: "1. trace an arc" "2. trace another arc" "3. how does this look so wrong" "4. just eyeball it"
[10] Angle bisector: "1. trace two arcs" "2. more arcs" "3. even more arcs" "4. all is arcs" "5. help me"
[15] Regular 17-gon: "1. read directions" [a dense Wikipedia construction] "2. blank stare" "3. cheat" [Google search: "picture of regular 17-gon"] "4. pretend you did it"
[19] Venn diagram: "1. draw circle" "2. draw other circle" "3. add labels": Origami (infuriating because hard to do) · Faulkner (infuriating because hard to understand) · overlap: drawing with compass
[22] Cantor ternary set: "1. take pointy end of compass" "2. stab eyes" "3. now everything looks like Cantor ternery set" "wow… I nailed it…"
Content note: The Cantor set joke is 'stab eyes' with the compass point (cartoon violence).
Use this cartoon
Free for classrooms, worksheets, slides and other non-commercial use under CC BY-NC 4.0, with credit to Ben Orlin.
Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2018-01-10-compass-constructions-made-easy/ (CC BY-NC 4.0)