Illustration showing a line that remains parallel to a given line, and touches at one end a given circumference.

Illustration showing a line that moves so that its ends constantly touch two fixed lines which are perpendicular…

Illustration of a circle inscribed in a regular nonagon. This could also be described as a regular nonagon…

Illustration used to show how to inscribe a regular octagon in a given circle.

Problem exercise in drawing a development or a stretchout image of the octagonal roof and finding the…

Oval with dotted vertical and horizontal lines that are lines of symmetry.

An illustration showing how to construct a pentagon inscribed in a circle. "Draw the diameter AB, and…

Illustration used to show how to inscribe a regular pentagon in a given circle.

An illustration showing how to construct a pentagon on a given line. "From B erect BC perpendicular…

Regular pentagon inscribed in a circle, circumscribed about a circle.

Illustration of a cyclic pentagon, a pentagon inscribed in a circle. This can also be described as a…

Illustration of pentagon inscribed in circle. Or, circle circumscribed about pentagon. Construction…

Illustration showing a circle inscribed in a regular pentagon. Or, a regular pentagon circumscribed…

Illustration of a circle with center O and diameters AB and CD perpendicular to each other.

Diagram used to prove the theorem: "Every section of a sphere by a lane is a circle."

Illustration used to show how to inscribe any regular polygon in a given circle.

Two arrangements of pulley: crossed belt and uncrossed belt. The pulleys are constructed with two circles…

Illustration of a cyclic quadrilateral, a quadrilateral inscribed in a circle. This can also be described…

Illustration used to draw lines which are radii of a circle where the center is inaccessible.

Illustration of a circle inside of a rectangle. The two figures have the same center.

"In ordinary work the usual way of rectifying an arc is to step around it with the dividers, in spaces…

Illustration of a regular heptagon/septagon circumscribed about a circle. This can also be described…

Illustration used to show how to draw a regular polygon when given a side of the polygon.

Illustration of ring (small circle in larger concentric circle) with piece cut out.

Illustration of ring (small circle in larger concentric circle) sprung into place.

Circular rosette with 12 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 12 petals. It is made by rotating circles about a fixed point. The radii of the…

Circular rosette with 16 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 16 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 24 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 24 petals. It is made by rotating circles about a fixed point. The radii of the…

Circular rosette with 3 petals. It is made by rotating circles about a fixed point. The radii of the…

Circular rosette with 32 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 32 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 6 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 48 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 6 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 6 petals. It is made by rotating circles about a fixed point. The radii of the…

Circular rosette with 8 petals in a circle. It is made by rotating circles about a fixed point. The…

Circular rosette with 8 petals in a circle. It is made by rotating circles about a fixed point. The…

An illustration showing a circle sector with radius r, center/central angle v, and length of circle…

An illustration showing a circle sector with center/central angle v and polygon angle w.

Illustration of a circle used to prove "Any angle inscribed in a semicircle is a right angle."

A sphere with arcs and poles. "The distance of all points in the circumference of a circle of a sphere…

"Every section of a sphere made by a plane is a circle."

Diagram used to prove the theorem: "All points in the circumference of a circle of a sphere are equally…

Illustration of a sphere generated by the revolution of a semicircle ACB about its diameter AB as an…

Illustration of a sphere with a tangent plane. "A plane perpendicular to a radius at its extremity is…