Illustration showing four angles that can be used to define different relationships, such as adjacent,…

Illustration showing six angles that can be used to define different relationships, such as adjacent,…

An illustration showing when one straight line meets another straight line and makes the adjacent angles…

Illustration of the superposition of two angles to compare magnitudes of the same kind.

Illustration of supplementary angles. Two angles whose sum is a straight angle.

Illustration of supplementary angles. Two angles whose sum is a straight angle. This can be used tow…

Illustration of supplementary angles. Two angles whose sum is a straight angle. This can be used tow…

Illustration showing angles 1 and 2 are supplementary and angles ACD and DCB are supplementary. Also,…

Vertical angles are when two angles have the same vertex, and the sides of the one are prolongations…

Illustration showing that angles 1 and 2 are vertical and angles 3 and 4 are vertical.

"Hexagonal; tri-pyramidal. Crystals usually long prismatic in habit; sometimes short prismatic or tabular.…

"Hexagonal; tri-pyramidal. Crystals usually long prismatic in habit; sometimes short prismatic or tabular.…

"Tetragonal. Usually shows a combination of prism of second order, pyramid of first and basal plane."…

"Orthorhombic. Acicular pyramidal; consisting of a prism terminated by a combination of a very steep…

"Orthorhombic. Tabular; consisting of prominent brachypinacoid faces modified by a prism and a low brachydome."…

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…

"In the triangle above, the line AB is its altitude. Since we know how to find the area of one triangle,…

Illustration showing how to find the area of a hexagon using the triangles that make it up.

"It is found that the cord covering the curved surface is twice as long as the one covering the flat…

"The bases of the pyramids are considered as forming the surface of the sphere, while the altitude of…

"Orthohombric. Usually in tabular diamond-shaped crystals, formed by a short prism terminated by low…

"A crystal has a center of symmetry if an imaginary line is passed from some point on its surface through…

"Orthohombic. Crystals usually tabular parallel to base; often diamond shaped because of the presence…

"Orthohombic. Crystals usually tabular parallel to base; often diamond shaped because of the presence…

"Hexagonal. Strong prismatic habit. Frequently vertically striated and grooved. Forms usually present…

"Hexagonal. Strong prismatic habit. Frequently vertically striated and grooved. Forms usually present…

Illustration showing that the bisector of a given angle is the locus of points equidistant from the…

Illustration showing that the perpendicular bisector of a given line is the locus of points equidistant…