Proof: By Euclid
(related to Corollary: 3.16: Line at Right Angles to Diameter of Circle At its Ends Touches the Circle)
This follows immediately from the Prop 3.16.
Adapted from CC BY-SA 3.0 Sources:
- Callahan, Daniel: "Euclid’s 'Elements' Redux" 2014
Adapted from (Public Domain)
- Casey, John: "The First Six Books of the Elements of Euclid"