Circle modeling the earth. O is the center of the earth, r the radius of the earth, and h the height…

Illustration showing a circle with a diameter, radius, lines, triangle, and segment drawn.

Illustration of a circle with an angle inscribed in a segment greater than a semicircle, an acute angle.

Illustration of a circle with an angle inscribed in a segment less than a semicircle, an obtuse angle.

Illustration of a circle with a right angle inscribed in a semicircle.

Illustration showing a circle with equilateral triangles and another circle within.

Illustration of circle with radius of 4000, and triangle with 45 degree angle enclosed.

Illustration of a 6-point star created by two equilateral triangles (often described as the Star of…

Illustration of triangle inscribed in circle. Or, circle circumscribed about triangle.

Illustration showing a circle with an inscribed triangle and radii.

Illustration showing that a circle may be considered as made up of triangles whose bases form the circumference.

Illustration showing a circle with an inscribed quadrilateral and triangles formed by extended chords.

Illustration showing that from any point in the circumference of a circle, a chord and a tangent are…

Illustration showing 2 intersecting circles with a lines drawn that form a triangle.

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"If a cone be cut by a plane, parallel to the base, so as to form two parts, the lower part is called…

Illustration of a plane passing through the vertex of a cone (section made is a triangle).

Illustration of a plane passing through the vertex of a cone (section made is a triangle).

Two dimensional view of the cuts required to create the conic sections hyperbola, parabola, ellipse,…

The Renaissance console is shaped in front-view like a pendant triangle. This console is found in a…

Illustration of a triangle with its incircle and three excircles constructed.

Illustration of the construction used to make a triangle when given two sides and the angle opposite…

Illustration of the construction used to make a triangle when given two sides and the angle opposite…

Illustration of the construction used to make a triangle when given two sides and the angle opposite…

Illustration used to construct a triangle , given the perimeter, one angle, and the altitude from the…

Illustration showing the correct and incorrect position of a right line pen against a T-square, triangle,…

"Draw three-inch square. Draw lines AB, BC, DE and EF at 30 degrees. Divide lower side into seven equal…

"This triangular shape is a good one also for a movable poultry-house in its simplest form." —…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures…

Illustration of blueprint used by highway engineers to widen the pavement on the inside of the curve…

A homemade section liner device made by slipping a wooden block to hold the triangle to make cross hatching…