Unit 7, Lesson 1

Relationships of Angles

Grade 7

1.1

Warm-up

Which angle is bigger?
Identify an obtuse angle in the diagram.

1.2

Activity

1.3

Activity

1.4

Activity

Tyler and Priya were both measuring angle .

A protractor is pictured. An acute angle has T at 0 or 180 degrees, vertex at the center of the protractor, and S at the end of a line through 40 or 140 degrees.

Priya thinks the angle measures 40 degrees. Tyler thinks the angle measures 140 degrees. Do you agree with either of them? Explain your reasoning.

Student Lesson Summary

When two lines intersect and form four equal angles, we call each one a right angle. A right angle measures . You can think of a right angle as a quarter turn in one direction or the other.

Two lines meet to form four angles. Each angle is marked 90 degrees, and with the symbol for perpendicular lines.

An angle in which the two sides form a straight line is called a straight angle. A straight angle measures . A straight angle can be made by putting right angles together. You can think of a straight angle as a half turn, so that you are facing in the opposite direction after you are done.

A straight line is indicated to be an angle with measure 180 degrees.

If you put two straight angles together, you get an angle that is . You can think of this angle as turning all the way around so that you are facing the same direction as when you started the turn.