Illustration showing two equal triangles. This can be used to show that two triangles are equal if the…

Illustration showing two equal right triangles. This can be used to show that two right triangles are…

Illustration of a triangle divided by a parallel line to form two similar triangles.

Illustration showing three triangles. This is used to show the following theorem: If two triangles have…

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…

"The trisoctahedron is a form composed of twenty-four isosceles triangular faces, each of which intersects…

"The faces of the tristetrahedron correspond to one-half the faces of a trapezohedron." — Ford,…

An illustration showing how to construct two circles that tangent themselves and two given lines. "Draw…

"The cone B would be developed by cutting a right section as S—S whose stretchout will be a circle…

"If the cylinder A were to be developed a right section as at S—S would have to be taken, whose…

"The intersection of two cylinders might represent a dome on a boiler. If the top view of cylinder A…

Illustration of a vertical line segment. A line segment is a section of a line with definite endpoints.

Illustration of a vertical line segment. A line segment is a section of a line with definite endpoints.…

"Tetragonal. Prismatic in habit. Often vertically striated. Common forms are prisms of first and second…

"Tetragonal. Prismatic in habit. Often vertically striated. Common forms are prisms of first and second…

"Tetragonal; tripyramidal. Crystals usually prismatic. Prominent forms are prisms of the first and second…

"Tetragonal; tripyramidal. Crystals usually prismatic. Prominent forms are prisms of the first and second…

"A crystal of zincite with a prism terminated by a pyramid above a basal pinacoid below." — Ford,…

"Tetragonal. Crystals usually show a simple combination of prism and pyramid of the first order. The…