Geometry Definitions

Front 1

Point

Back 1

A location in space. Represented wih a dot and a single capital letter.

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Line

Back 2

All points that lie on a straight, unbroken path.

Front 3

Line Segment

Back 3

A line with 2 endpoints.

Front 4

A Ray

Back 4

A line that has one endpoint and extends forever in one direction.

Front 5

Angle

Back 5

A figure formed by 2 rays that don't lie on the same line but have the same endpoint

Front 6

Postulate

Back 6

A mathematical statement assumed to be true.

Front 7

Theorem

Back 7

A statement that is true only after it is proven through a series of logical steps

Front 8

Proof

Back 8

A logical structure of reasoning that begins from accepted ideas and proceeds through logic to reach a conclusion which makes a theorem.

Front 9

Number line

Back 9

A line where every point corresponds to a real number and every real number corresponds to a point.

Front 10

Cordinate of a point

Back 10

The real number that corresponds to that point on a number line.

Front 11

Vertex of an angle

Back 11

The common endpoint of an angle; Plural: Vertice.

Front 12

Obtuse angle

Back 12

An angle whose measure is greater than 90 degrees.

Front 13

Straight angle

Back 13

An angle whose measure is 180 degrees.

Front 14

Acute angle

Back 14

An angle whose measure is less than 90 degrees.

Front 15

Angle Congruence Postulate

Back 15

If 2 angles have the same measure, they they are congruent. Also if they are congruent, they have the same measure.

Front 16

Adjacent angle

Back 16

Are angles that are in the same plane and have a common vertex and common side, and have no interior points in common.

Front 17

Complemantary angles

Back 17

2 angles whose sum is 90 degrees when you add the measures of both angles.

Front 18

Supplementary angles

Back 18

2 angles whose measurement is 180 degrees when you add both measurements of the 2 angles.

Front 19

Linear pair of angles

Back 19

A pair of angles that are formed if the endpoint of a ray is on a line, creating 2 angles; they must share a common side

Front 20

Parallel lines

Back 20

Coplanar lines that never intersect.

Front 21

Perpendicular lines

Back 21

Lines that meet at right angles.

Front 22

Segment bisector

Back 22

Is a ray, line segment, or a line that divides an angle into 2 congruent angles.

Front 23

Circumscribed

Back 23

Encircling and touching each vertex of another figure.

Front 24

Inscribed circle

Back 24

A circle inside a figure and touching exactly one point on each side of the figure.

Front 25

Circumcenter

Back 25

The point at which the 3 perperdicular bisectors of a triangle intersect.

Front 26

Median of a triangle

Back 26

A segment drawn from the vertex of a triangle to the midpoint of its opposite side, and it divides the triangle into 2 equal sides.

Front 27

Centroid

Back 27

The center of gravity of the triangle.

Front 28

Pre image

Back 28

The original figure before it is transformed.

Front 29

Image

Back 29

The result of a transformation.

Front 30

Isometric transformations

Back 30

Transformations that preserve the size and shape of the pre-image.

Front 31

Reflection

Back 31

A type of transformation. The flipping of a figure.

Front 32

Rotation

Back 32

A type of transformation. The turning of a figure.

Front 33

Translation

Back 33

A type of transformation. The sliding of a figure in a straight path without rotation or reflection.

Front 34

Dilation

Back 34

The shrinking or expanding of a figure; this does not preserve the size of the pre-image, therefore it is not an isometric transformation.

Front 35

X-axis

Back 35

The horizontal number line on a coodinate plane.

Front 36

Y-axis

Back 36

The vertical number line on a coodinate plane.

Front 37

Inductive reasoning

Back 37

A type of reasoning that is based on observations of patterns and past events.

Front 38

Deductive reasoning

Back 38

A type of reasoning that uses previously proven or accepted properties to reach conclusions.

Front 39

Argument

Back 39

A set of statements called premises, that are used to reach a conclusion.

Front 40

Conditional statement

Back 40

A statement in the form of P, then Q in which they hypothesis implies the conclusion.

Front 41

Negate

Back 41

To change a meaning to its opposite. The result is know as the inverse of the original statement.

Front 42

Converse

Back 42

When you switch the hypothesis and the conclusion.

Front 43

Contrapositive

Back 43

When you combine the converse with the inverse of the original statement.

Front 44

Truth-functionally equivalent

Back 44

A characteristic describing a pair of statements that have identical truth tables.

Front 45

Law of contrapositive

Back 45

A conditional statement is true if and only if its contrapositive is true.

Front 46

Euler diagram

Back 46

A diagram with an outer circle enclosing an inner circle, which might enclose another inner cirlce, and soon, representing how conditional statements are related to each other.

Front 47

Logical chain

Back 47

A chain of premises that lead to a logical conclusion; logical chains are represented by several circles within the Euler diagram.

Front 48

Compund statement

Back 48

A statement that connects 2 statements with either the word 'and' or 'or'.