Euclid:Proposition/XIII/18/Lemma

Proposition

In the words of Euclid:

But that the angle of the equilateral and equiangular pentagon is a right angle and a fifth we must prove thus.

(The Elements: Book $\text{XIII}$: Proposition $18$ : Lemma)

Sources

• 1926: Sir Thomas L. Heath: Euclid: The Thirteen Books of The Elements: Volume 3 (2nd ed.) ... (previous) ... (next): Book $\text{XIII}$. Propositions