Geometry Problem 655: Archimedes' Book of Lemmas: Proposition 15 - Circle, Regular Pentagon, Radius

Let AB be the diameter of a circle, BC a side of an inscribed regular pentagon, D the midpoint of the arc BC. AB and CD meet in E; AD and BC meet in F. If FG is perpendicular to AB, then EG is equal to the radius of circle.

  

Books of Lemmas Index

Proposition 1
Proposition 2
Proposition 3
Proposition 4
Proposition 5
Proposition 6
Proposition 7
Proposition 8
Proposition 9
Proposition 10
Proposition 11
Proposition 12
Proposition 13
Proposition 14
Proposition 15