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

Diagram 12.

LESSON TWELFTH.

REVIEW.

Read five lines that are perpendicular to the line a b. (Diagram [12].)

Five that are perpendicular to c d.

Two that are perpendicular to u v, and meet it. Three that do not meet it.

Why are o p and m n perpendicular to each other?

When are lines said to be perpendicular to each other?