We noted in the text that our methods for measuring distance led to a prescription for drawing a circle that is basically the same as Euclid's method using a compass. A straight line can be drawn from any point to any point. One can describe a circle with any center and radius.
All right angles are equal to one another.
If a straight line falling on two straight lines makes the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, meet on that side on which the angles are less than two right angles. A corner reflector utilizes two mirrors at right angles to each other to send light back in the direction from whence it came. Prove that the path travelled by the light satisfies Euclid's Fifth Postulate. Corner reflector 4. Consider relaxing some of the axioms for classical particles.