A point has no dimension.

It is usually represented by a small dot.

•A

Point A

Basics of GeometryDefining Terms

A line extends without end in two directions. It is usually represented by a straight line with two arrowheads to indicate that the line . line AB

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line BA�������������� �

line

. A plane extends in two dimensions. It is usually represented by a shape that looks like a table or a wall, however you must imagine that the plane extends without end

The ray AB (symbolized by ) ) consists of the initial point A and all points on ABthat lie on the same side of A as point B.

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Note that AB and BA are NOT the same ray.����������������������������

The first letter must indicate the starting point of the ray.

If C is between A and B, then CAand CB are opposite rays.

Like points, segments and rays are collinear if they lieon the same plane. So, any two opposite rays arecollinear. Segments, rays, and lines are coplanar if they lie on the same plane.

The line segment or segment AB

(symbolized by AB) consists of the

endpoints A and B, and all points on AB

that are between A and B.

Consider the line AB (symbolized by AB).

Angle– two rays with a common initial point.– the rays are called the sides of the angle.– the common initial point is called the vertex.

vertexsides

Classifying Angles

Acute AnglesAngles with a measure between 0o and 90o.

A0 90m A

Classifying Angles

Acute AnglesAngles with a measure between 0o and 90o.

Right AnglesAngles with a measure of exactly 90o.

A

90m A

Acute AnglesAngles with a measure between 0o and 90o.

Right AnglesAngles with a measure of exactly 90o.

Obtuse AnglesAngles with a measure between 90o and 180o.

Classifying Angles

A

90 180m A

Acute AnglesAngles with a measure between 0o and 90o.

Right AnglesAngles with a measure of exactly 90o.

Obtuse AnglesAngles with a measure between 90o and 180o.

Straight AnglesAngles with a measure of exactly 180o.

Classifying Angles

A

180m A

Collinear Points– points that lie on the same line

Non-collinear Points– points that do not lie on the same line

A B

D

Coplanar points are points that lie on the same plane.

Plane M or plane ABC

AC

MB

Perpendicular Lines are two lines that intersect to form a right angle.

Equidistant is having the same distance from a point or a line.

Q

S

P

Equidistant from Two PointsA point that has the same measureto each of two other points.

P is equidistantfrom Q and S

because PQ PS

P

m

Distance from a Point to a LineThe length of a perpendicular segmentfrom the point to the line.

M

the distancefrom P to line m

is PMQ

R

the distancefrom Q to line m

is QR

Points P and Q are equidistant from line m.

Congruent Figures• Two geometric figures are congruent if they

have exactly the same size and shape

Similar Figures• Two geometric figures are similar if the corresponding

angles are congruent and corresponding sides are proportional.