Definition:Angle/Rectilineal

From ProofWiki
Jump to: navigation, search

Definition

In the words of Euclid:

And when the lines containing the angle are straight, the angle is called rectilineal.

(The Elements: Book $\text{I}$: Definition $9$)


Thus the distinction is made between straight-line angles and curved-line angles.

Most of the time the fact that angles are rectilineal is taken for granted.


Also known as

The term is also seen as rectilinear.