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

And the angle Green measures the direction of the line g b from the line e f.

Then the lines g b, h d, have the same direction, and are parallel.

TEST LESSON.

1. Prove the same without the colors.

2. Prove the same, using the angle f h d.

3. Prove the same, supposing the angles a g h, g h c, equal to two right angles, and using the angle a g e.

4. Prove the same, using the angle c h f.

See Note [E], Appendix.

PROPOSITION VIII. THEOREM.

The following demonstration is very easy. Read it once, and see if you can go through it without a second reading:—