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

6. Prove the opposite exterior and interior angles a m n, d n f, equal.

7. Prove the opposite exterior and interior angles e m b, m n c, equal.

8. Prove the opposite exterior and interior angles b m n, c n f, equal.

Diagram 39.

PROPOSITION IV. THEOREM.

DEVELOPMENT LESSON.

What do you know of the opposite exterior and interior angles Red, Yellow?

What do you know of the vertical angles Red, Green?

Then if the interior alternate angles Green, Yellow, are separately equal to the angle Red, what new fact do you know?