Euclid:Proposition/XI/21

Proposition

In the words of Euclid:

Any solid angle is contained by plane angles less than four right angles.

(The Elements: Book $\text{XI}$: Proposition $21$)

Sources

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