Viviani's curve
Construction of Viviani's curve inspired by Villalpando's proportionatrix secunda (as Viviani claims) in a semicircle of diameter AC. Steps to find a point K of the curve from a point F of the semicircle:
- Semicircle of diameter AC (see diagram).
- A point F on the large semicircle is selected and FC drawn.
- FC is drawn.
- FL is perpendicular to AC.
- LK is perpendicular to CF.
- Unite AF.