BASIC ELEMENTS OF GEOMETRY

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GEOMETRIC TERMSBasic Elements of Geometry

Point

Definition: a location in space.

A point is named by a capital letter, and its location may be indicated by a dot.

Write: ASay: Point A

Point

A point is named by its coordinates, and its location may be indicated by a dot.

Write: PSay: Point P

Line

Definition: a set of points that form a straight path extending infinitely in two directions. The directions are opposite of each other.

Write: Say: Line AB

Line Segment

Definition: a part of a line that has two endpoints and a definite length

A BWrite: Say: Line segment AB

AB

Ray

Definition: a set of points that has one endpoint and extends infinitely in one direction

A B C

Write: Say: Ray AB or Ray AC

or AB ACuuur uuur

Angle

Definition: a geometric figure made up of two rays of two line segments that have the same endpoint. The common endpoint is the vertex.

Write: Say: Angle ABC or Angle B

ABC or B

Plane

Definition: a flat surface that extends without end (infinitely) in all directions.

Write: Plane ASay: Plane A A

ANGLESBasic Elements of Geometry

Angle

Definition: a geometric figure made up of two rays of two line segments that have the same endpoint. The common endpoint is the vertex.

ACUTE ANGLE

Angles that have a measure that is less than 90 degrees.

RIGHT ANGLE

Angles that have a measure that is exactly 90 degrees.

OBTUSE ANGLE

Angles that have a measure that is greater than 90 degrees but less than 180 degrees.

STRAIGHT ANGLE

Angles that have a measure that is exactly 180 degrees.

TRIANGLESBasic Elements of Geometry

Triangle

Definition: a geometric figure made up of three rays or three line segments.

Write: Say: Triangle ABC or Triangle BCA or Triangle CAB

or ABC BCA or CBAV V V

ACUTE TRIANGLE

A triangle composed of three acute angles.

RIGHT TRIANGLE

A triangle composed of one right angle and two acute angles.

OBTUSE TRIANGLE

A triangle composed of one obtuse angle and two acute angles.

SCALENE TRIANGLE

A triangle with no congruent sides and no congruent angles.

ISOSCELES TRIANGLE

A triangle with at least two congruent sides and at least two congruent angles.

EQUILATERAL TRIANGLE

A triangle with three congruent sides and three congruent angles.

QUADRILATERALSBasic Elements of Geometry

Quadrilateral

Definition: a geometric figure made up of four sides and four angles

RECTANGLE

A quadrilateral with four right angles.Opposite sides are equal in length.

SQUARE

A quadrilateral with four right angles.All sides are equal in length.

PARALLELOGRAM

A quadrilateral with opposite sides that are parallel.Opposite sides are equal and opposite angles are equal.

RHOMBUS

A quadrilateral with opposite sides that are parallel.Opposite sides are equal in length and opposite angles are equal in measure. All sides are equal in length.

TRAPEZOID

A quadrilateral with two sides are parallel and two sides are not parallel.

KITE

A quadrilateral with two pairs of consecutive congruent sides.

SYMBOLS AND ABBREVIATIONSBasic Elements of Geometry

COMMON POLYGONSBasic Elements of Geometry