Marks' first lessons in geometry / In two parts. Objectively presented, and designed for the use of primary classes in grammar schools, academies, etc.

by Bernhard Marks

Are they adjacent to each other?

Are they vertical angles?

Then they are alternate angles.

Alternate angles lie on different sides of the intersecting line, and are neither adjacent nor vertical.

Are the alternate angles b m n, m n c, exterior or interior?

Then they are called “interior alternate angles.”

Read another pair of interior alternate angles between a b and c d.

Are the angles e m b, c n f, alternate angles? Why?

Are they exterior or interior?

Then what may they be called?