Euclid:Proposition/VI/19/Porism

Proposition

In the words of Euclid:

From this it is manifest that, if three straight lines be proportional, then, as the first is to the third, so is the figure described on the first to that which is similar and similarly described in the second.

(The Elements: Book $\text{VI}$: Proposition $19$ : Porism)

Sources

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