ClipArt ETC
A protractor indicating a measurement of 60 degrees from the right side.

Protractor, 60 Degrees

A protractor indicating a measurement of 60 degrees from the right side.

A protractor indicating a measurement of 65 degrees.

Protractor, 65 Degrees

A protractor indicating a measurement of 65 degrees.

A protractor indicating a measurement of 65 degrees from the right side.

Protractor, 65 Degrees

A protractor indicating a measurement of 65 degrees from the right side.

A protractor indicating a measurement of 70 degrees.

Protractor, 70 Degrees

A protractor indicating a measurement of 70 degrees.

A protractor indicating a measurement of 70 degrees from the right side.

Protractor, 70 Degrees

A protractor indicating a measurement of 70 degrees from the right side.

A protractor indicating a measurement of 75 degrees.

Protractor, 75 Degrees

A protractor indicating a measurement of 75 degrees.

A protractor indicating a measurement of 75 degrees from the right side.

Protractor, 75 Degrees

A protractor indicating a measurement of 75 degrees from the right side.

A protractor indicating a measurement of 80 degrees.

Protractor, 80 Degrees

A protractor indicating a measurement of 80 degrees.

A protractor indicating a measurement of 80 degrees from the right side.

Protractor, 80 Degrees

A protractor indicating a measurement of 80 degrees from the right side.

A protractor indicating a measurement of 85 degrees.

Protractor, 85 Degrees

A protractor indicating a measurement of 85 degrees.

A protractor indicating a measurement of 85 degrees from the right side.

Protractor, 85 Degrees

A protractor indicating a measurement of 85 degrees from the right side.

A protractor with 90 and 90 degree suplementary angles indicated.

Protractor, 90 and 90 Degrees

A protractor with 90 and 90 degree suplementary angles indicated.

A protractor indicating a measurement of 90 degrees.

Protractor, 90 Degrees

A protractor indicating a measurement of 90 degrees.

A protractor indicating a measurement of 90 degrees from the right side.

Protractor, 90 Degrees

A protractor indicating a measurement of 90 degrees from the right side.

A protractor indicating a measurement of 95 degrees.

Protractor, 95 Degrees

A protractor indicating a measurement of 95 degrees.

A protractor indicating a measurement of 95 degrees from the right side.

Protractor, 95 Degrees

A protractor indicating a measurement of 95 degrees from the right side.

"An orthorhombic pyramid has eight triangular faces, each of which intersects all three of the crystallographic axes." — Ford, 1912

Pyramid

"An orthorhombic pyramid has eight triangular faces, each of which intersects all three of the crystallographic…

"The dihexagonal pyramid is a form of twenty-four isoceles triangular faces, each of which intersects all three of the horizontal axes differently and intersects also the vertical axis." — Ford, 1912

Dihexagonal pyramid

"The dihexagonal pyramid is a form of twenty-four isoceles triangular faces, each of which intersects…

"The ditetragonal pyramid is a form composed of sixteen isoceles trianglular faces, each of which intersects all three of the crystallographic axes, cutting the two horizontal axes at different lengths." — Ford, 1912

Ditetragonal pyramid

"The ditetragonal pyramid is a form composed of sixteen isoceles trianglular faces, each of which intersects…

"The pyramid of the first order is a form consisting of eight isoceles triangular faces, each of which interesects all three crystallographic axes, the intercepts upon the two horizontal axes being equal." — Ford, 1912

First order pyramid

"The pyramid of the first order is a form consisting of eight isoceles triangular faces, each of which…

"Crystal faces are described according to their relations to the crystallographic axes. A series of numbers which indicate the relative distances by which a face intersects the different axes are called its parameters. " — Ford, 1912

Orthorhombie pyramid

"Crystal faces are described according to their relations to the crystallographic axes. A series of…

"The pyramid of the second order is a form composed of eight isoceles triangular faces, each of which intersects one horizontal axis and the vertical axis and is parallel to the second horizontal axis." — Ford, 1912

Second order pyramid

"The pyramid of the second order is a form composed of eight isoceles triangular faces, each of which…

"The symmetry of the Pyritohedral class is as follows: The three crystal axes of binary symmetry; the four diagonal axes, each of which emerges in the middle of the octant, are axes of trigonal symmetry." — Ford, 1912

Symmetry of pyritohedral class

"The symmetry of the Pyritohedral class is as follows: The three crystal axes of binary symmetry; the…

"This form consists of twelve pentagonal-shaped faces, each of which intersects one crystallographic axis at unity, the second axis at some multiple, and is parallel to the third." — Ford, 1912

Pyritohedron

"This form consists of twelve pentagonal-shaped faces, each of which intersects one crystallographic…

"A combination of pyritohedron and octahedron." — Ford, 1912

Pyritohedron and octahedron

"A combination of pyritohedron and octahedron." — Ford, 1912

"A cube trunctuated with pyritohedron and octahedron." — Ford, 1912

Pyritohedron, cube, and octahedron

"A cube trunctuated with pyritohedron and octahedron." — Ford, 1912

Pyroxene

Pyroxene

Pyroxene

Pyroxene

Pyroxene

Pyroxene

Illustration of a quadrilateral with diagonals AC and BD.

Quadrilateral With Diagonals

Illustration of a quadrilateral with diagonals AC and BD.

An example of a quadrilateral used to find its area.

Area of Quadrilaterals

An example of a quadrilateral used to find its area.

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally developed as to give the effect of a hexagonal pyramid." — Ford, 1912

Quartz

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally…

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally developed as to give the effect of a hexagonal pyramid. Sometimes one rhombohedron predominates or occurs alone." — Ford, 1912

Quartz

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally…

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally developed as to give the effect of a hexagonal pyramid. Sometimes one rhombohedron predominates or occurs alone. At times the prism faces are wanting, and the combination of the two rhombodendrons gives what appears to be a doubly terminated hexagonal pyramid, known as a quartzoid." — Ford, 1912

Quartz

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally…

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to be observed trunctuating the edges between prism and rhombohedron." — Ford, 1912

Left-handed quartz

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to…

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to be observed trunctuating the edges between prism and rhombohedron." — Ford, 1912

Right-handed quartz

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit lieing down.

Rabbit Lieing Down

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit lieing down.

Rabbit Lieing Down

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit lying down.

Rabbit Lying Down

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit lying down.

Rabbit Lying Down

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit siting on its hind legs.

Rabbit Siting on Its Hind Legs

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit siting on its hind legs.

Rabbit Siting on Its Hind Legs

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit siting on its hind legs.

Rabbit Siting on Its Hind Legs

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rabbit siting on its hind legs.

Rabbit Siting on Its Hind Legs

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

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points down.

Ray Pointing Down

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points down and toward the left.

Ray Pointing Down and Left

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points down and toward the right.

Ray Pointing Down and Right

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points toward the left.

Ray Pointing Left

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points toward the right.

Ray Pointing Right

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points up.

Ray Pointing Up

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points up and toward the right.

Ray Pointing Up and Right

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration points up and toward the left.

Ray Pointing Up and Right

A ray has one endpoint and extends indefinitely in the other direction. The ray in this illustration…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing left.

Reclining Man Facing Left

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing left.

Reclining Man Facing Left

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing left.

Reclining Man Facing Left

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing left.

Reclining Man Facing Left

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing right.

Reclining Man Facing Right

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing right.

Reclining Man Facing Right

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing right.

Reclining Man Facing Right

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a reclining man facing right.

Reclining Man Facing Right

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 consisting of triangles, squares, and parallelograms are used to construct the given shape. This tangram depicts a rectangle.

Rectangle

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