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

How much less than a right angle is f n i?

Diagram 11.

LESSON ELEVENTH.

RELATIONS OF LINES.

PERPENDICULAR LINES.

What kind of angles do the lines a b and c d make with each other? (Diagram [11].)

Then they are perpendicular to each other.

What line is perpendicular to x y?