Illustration used to prove the theorem "If three or more parallel lines intercept equal segments on…

Illustration of a circle with parallels intercepting equal arcs on a circumference.

Illustration used to show how to divide a given straight line into any number of equal parts.

Illustration used to prove "The line joining the mid-points of two sides of a triangle is parallel to…

An illustration showing the construction used to erect a parallel line. "With C as a center, draw the…

"If one of two parallels is perpendicular to a plane, the other is also."

Illustration of three intersecting planes. "The intersections of two parallel planes by a third plane…

Illustration of three intersecting planes. "The straight line perpendicular to one of two parallel lanes…

"If two straight lines are cut by three parallel planes, the corresponding segments are proportional."

"If two angles not in the same plane have their sides respectively parallel and lying in the same direction,…

"If two intersecting lines are each parallel to a given plane, the plane of these lines is parallel…

Illustration used to prove "The line bisecting one side of a triangle and parallel to another side bisects…

Illustration used to prove the theorem "The line bisecting one of the non parallel sides of a trapezoid…