- Why
**bicontinuity**is the right condition for topological equivalence (homeomorphism): if continuity of the inverse isn’t required, then a circle could be equivalent to a line (.99999 and 0 would be neighbours) — Minute 8 or so. - Geometric construction (no complex numbers) of the circle group.
- Pappos’ theorem. (Minute 31)
- Pascal’s theorem.
- Desargues’ theorem.

Hat tip to +Ozymandias Haynes.

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