2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 intersecting lines.

Intersecting Lines, 2

2 intersecting lines.

2 line segments, AB and CD. AB is half the length of CD.

Segments, 2 Line

2 line segments, AB and CD. AB is half the length of CD.

2 lines that are intersected by a third line known as a transversal.

Transversal, 2 Lines Intersected By A

2 lines that are intersected by a third line known as a transversal.

2 parallel horizontal line segments.

Segments, 2 Parallel Line

2 parallel horizontal line segments.

2 slanted parallel line segments.

Segments, 2 Parallel Line

2 slanted parallel line segments.

2 slanted parallel line segments.

Segments, 2 Parallel Line

2 slanted parallel line segments.

2 intersecting lines, one of which is vertical and one of which is horizontal. The intersection forms a right angle.

Intersecting Lines, 2 Perpendicular

2 intersecting lines, one of which is vertical and one of which is horizontal. The intersection forms…

Illustration used to prove the theorem "If three or more parallel lines intercept equal segments on one transversal, they intercept equal segments on any other transversal."

4 Parallel Lines Cut By 2 Transversals

Illustration used to prove the theorem "If three or more parallel lines intercept equal segments on…

3 lines which intersect at a common point.

Intersecting Lines, 3

3 lines which intersect at a common point.

3 parallel horizontal line segments.

Segments, 3 Parallel Line

3 parallel horizontal line segments.

Illustration of line segment AB, which is made up of line segments AC and CB. C is considered the midpoint of segment AB.

Segment, 3 Points on a Line

Illustration of line segment AB, which is made up of line segments AC and CB. C is considered the midpoint…

4 lines which intersect at a common point.

Intersecting Lines, 4

4 lines which intersect at a common point.

4 lines which intersect at a common point.

Intersecting Lines, 4

4 lines which intersect at a common point.

4 parallel horizontal line segments.

Segments, 4 Parallel Line

4 parallel horizontal line segments.

4 parallel lines cut by a 5th line known as the transversal.

Transversal, 4 Parallel Lines Cut By A

4 parallel lines cut by a 5th line known as the transversal.

5 parallel horizontal line segments.

Segments, 5 Parallel Line

5 parallel horizontal line segments.

6 parallel horizontal line segments.

Segments, 6 Parallel Line

6 parallel horizontal line segments.

6 slanted parallel line segments.

Segments, 6 Parallel Line

6 slanted parallel line segments.

6 slanted parallel line segments.

Segments, 6 Parallel Line

6 slanted parallel line segments.

8 lines which intersect at a common point.

Intersecting Lines, 8

8 lines which intersect at a common point.

"That point in which a right line drawn from the eye parallel to another given right line cuts the picture of plane."-Whitney, 1902

Accidental Point

"That point in which a right line drawn from the eye parallel to another given right line cuts the picture…

"Triclinic. Usually in tabular crystals parallel to brachypinacoid." — Ford, 1912

Albite

"Triclinic. Usually in tabular crystals parallel to brachypinacoid." — Ford, 1912

"Triclinic. Sometimes elongated parallel to b crystal axis." — Ford, 1912

Albite

"Triclinic. Sometimes elongated parallel to b crystal axis." — Ford, 1912

"Triclinic. Twinning very common, according to the albite law and evidenced by fine striation lines on the better cleavage surface." — Ford, 1912

Albite

"Triclinic. Twinning very common, according to the albite law and evidenced by fine striation lines…

Amphibole.

Amphibole

Amphibole.

Amphibole.

Amphinole

Amphibole.

"Monoclinic. Crystals prismatic in habit; the prism faces make angles of 55 and 125 degrees with each other." — Ford, 1912

Amphibole

"Monoclinic. Crystals prismatic in habit; the prism faces make angles of 55 and 125 degrees with each…

"Monoclinic. Crystals prismatic in habit; the prism faces make angles of 55 and 125 degrees with each other." — Ford, 1912"

Amphibole

"Monoclinic. Crystals prismatic in habit; the prism faces make angles of 55 and 125 degrees with each…

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 an angelfish.

Angelfish

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 an angelfish.

Angelfish

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 an angelfish.

Angelfish

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 an angelfish.

Angelfish

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

An illustration showing an angle the is less than a right angle. This is an acute angle.

Acute Angle

An illustration showing an angle the is less than a right angle. This is an acute angle.

Angle 3 is an acute angle.

Acute Angle

Angle 3 is an acute angle.

An illustration showing the construction used to divide an angle into two equal parts. "With C as a center, draw the dotted arc DE; with D and E as centers, draw the cross arcs at F with equal radii. Join CF, which divides the angle into the required parts."

Construction Of A Divided Angle

An illustration showing the construction used to divide an angle into two equal parts. "With C as a…

An illustration showing the construction used to divide an angle into two equal parts when the lines do not extend to a meeting point. "Draw the lined CD and CE parallel, and at equal distances from the lines AB and FG. With C as a center, draw the dotted arc BG; and with B and G as centers, draw the cross arcs H. Join CD, which divides the angle into the required equal parts."

Construction Of A Divided Angle

An illustration showing the construction used to divide an angle into two equal parts when the lines…

Illustration used to show "The two perpendiculars to the sides of an angle from any point in its bisector are equal."

Perpendiculars To The Sides Of An Angle

Illustration used to show "The two perpendiculars to the sides of an angle from any point in its bisector…

Illustration used to show "The two perpendiculars to the sides of an angle from any point not in its bisector are unequal."

Perpendiculars To The Sides Of An Angle

Illustration used to show "The two perpendiculars to the sides of an angle from any point not in its…

An illustration of a plane angle with vertex E and sides EF and ED.

Plane Angle

An illustration of a plane angle with vertex E and sides EF and ED.

An illustration showing a straight angle. When the sides of an angle extend in opposite directions, so as to be in the same straight line, the angle is called a straight angle.

Straight Angle

An illustration showing a straight angle. When the sides of an angle extend in opposite directions,…

Showing different types of angles: right, acute, and obtuse.

Angles

Showing different types of angles: right, acute, and obtuse.

Illustration showing that the sum of all the angles about a point equals 360°.

360° Sum of Angles

Illustration showing that the sum of all the angles about a point equals 360°.

Illustration showing two positive angles; angle 1 being the acute angle and angle 2 being the reflex angle.

Acute and Reflex Angles

Illustration showing two positive angles; angle 1 being the acute angle and angle 2 being the reflex…

An illustration showing acute, obtuse, straight, right, and reflex angles.

Acute, Obtuse, Straight, Right, And Reflex Angles

An illustration showing acute, obtuse, straight, right, and reflex angles.

An illustration of two angles that are adjacent. They have the same vertex and a common side between them. Angles BOD and AOD are adjacent

Adjacent Angles

An illustration of two angles that are adjacent. They have the same vertex and a common side between…

Angles 1 and 2 are adjacent angles. Two angles with a common vertex and a common side between them are adjacent angles.

Adjacent Angles

Angles 1 and 2 are adjacent angles. Two angles with a common vertex and a common side between them are…

Illustration of complementary angles. Two angles whose sum is a right angle.

Complementary Angles

Illustration of complementary angles. Two angles whose sum is a right angle.

Illustration showing that angles 1 and 2 are complementary.

Complementary Angles

Illustration showing that angles 1 and 2 are complementary.

Illustration showing that the difference between angle 1 and angle 2 is angle ABC.

Difference of Angles

Illustration showing that the difference between angle 1 and angle 2 is angle ABC.

Illustration used to prove that all right angles are equal.

Equal Right Angles

Illustration used to prove that all right angles are equal.

An illustration showing an angle the is greater than a right angle and less than a straight angle. This is an obtuse angle (solid curved arrow). The angle that is greater than a straight angle and less than two straight angles is called a reflex angle (dashed curved arrow).

Obtuse And Reflex Angles

An illustration showing an angle the is greater than a right angle and less than a straight angle. This…

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

Relationships Between 4 Angles

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