9.2 – Line Segments, Rays, and Angles Grade 4

Set the Purpose You know the names for different types of pairs of lines. Today, you will learn the special names for different types of angles. The hands on a clock meet at a point in the center of the clock. As they move, the size of the opening they make changes from minute to minute. What are some words you can use to describe the different openings?

Math Vocabulary A line segment is a part of a line with two endpoints. A ray is a part of a line that has one endpoint and continues on forever in one direction.

Angles An angle is a figure formed by two rays that have the same endpoint. A right angle is a square corner An acute angle is less than a right angle.

Angles An obtuse angle is greater than a right angle. A straight angle forms a straight line.

Practice What is this?

Practice Name four line segments. Name four rays. Name 2 right angles.

Homework Page 198 ( #1 – 14)