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

From the interior angles Blue, Yellow, take away the angle Blue: what remains?

From the adjacent angles Blue, Red, take away the same angle Blue: what remains?

What do you know of the two remainders?

The angle Red measures the direction of the line g b from what line?

The equal angle Yellow measures the direction of the line h d from what line?

Then if the lines g b, h d, have the same direction from the line e f, what do you call them?

Diagram 46.

DEMONSTRATION.

We wish to prove, that,