Lines, Segments, and Rays

Line

A line is perfectly straight and extends forever in both directions. Any two points on the line can be used to

name it

Line Segment

A line segment is part of a line between two points. The two points of the line segment are

used to name the line segment Line segments are congruent if they

have the same measure The symbol for congruence is ≈

Ray A ray is part of a line that starts at

an endpoint and extends forever in one direction.

A ray is named starting with its endpoint first and then any other point on the ray second

Intersecting Lines

Intersecting Lines are lines that cross at exactly one point. Lines l and m intersect at Q.

Perpendicular Lines

Perpendicular lines are lines that intersect to form 90° angles. The symbol ⊥ is used to denote

perpendicular lines. Line l ⊥ m

Parallel Lines

Parallel lines are lines that never intersect The symbol // is used to denote parallel

lines. Line l // m

Angles

Angles

An angle is formed by two rays sharing a common endpoint called a vertex.

ray

ray

vertex

The rays are the sides of the angle

The endpoint is the vertex

The name of the angle in the figure can be called <CAB

Classifying Angles

Acute Angles

Acute angles are angles that measure is greater than 0° and less than 90°.

Which angles are not acute?

1

23

4

5

Right Angles

Right angles are angles whose measure is exactly 90°. Which angle is a right angle?

1

23

4

5

Obtuse Angles

Obtuse angle are angles whose measure is greater than 90° and less than 180° Which angle is an obtuse angle?

1

23

4

5

Straight Angles

Straight angles are angles whose measure is exactly 180°. What’s another name for straight angles? Which is not a straight angle?

1 2

This is a ray. It only goes in one direction.

Adjacent Angles

Adjacent angles are angles that share a common vertex. Adjacent angles are next to each other? Which pair of angles are not adjacent?

2.

These angles are across from each other.

1.3.

4.

Vertical Angles

Vertical angles are opposite angles formed by interesecting lines. They are congruent. Which angles not vertical angles?

1. 4.

These are adjacent angles.

2. 3.

These are adjacent angles.

Supplementary Angles

Supplementary angles are angles whose sum is 180°. Which pair of angles are not

supplementary?

1. 2. 3. 4.

Complementary Angles Complementary angles are angles

whose sum is 90°. Which pair of angles are not

complementary?

1. 2. 3. 4.

Linear Pair

Linear Pair are two angles that form a straight line What is the sum of the angles? Which angles are not linear pairs?

1. 2. 3. 4.