# Villalpando's proportionatrix prima

Construction of the

*proportionatrix prima*in a semicircle of diameter AG. Steps to find a point K of the curve from a point F of the semicircle:- Semicircle of diameter AG and center D (see diagram).
- Semicircle of diameter DG.
- A point F on the large semicircle is selected and FG is drawn cutting the small semicircle in H.
- Circle of center G and radius GH.
- I is the intersection of AG with this circle.
- Circle of center I and radius IG.
- K is the intersection of this circle and FG.
- CK is perpendicular to AG.

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