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

Why are c e b and a e d called vertical angles?

What are vertical angles?

Read all the pairs of vertical angles formed by the lines h i, f g.

How many pairs of vertical angles are formed by the intersection of two lines?

Read all the pairs of vertical angles formed by the lines l m, n p.

LESSON NINTH.

KINDS OF ANGLES.

RIGHT ANGLES.

What do we call the angles a o c, c o b? (Diagram [9].)