2.  Name 3 examples of angles in the real
world.

3.  The ancient Babylonians created several
systems of measurement.
 Historians believe that they were the first
people to divide a circle into 360 equal
parts, called degrees.
 No matter who invented them, we all
use degrees to measure angles.

4.  90°
180° 0°
360°
270°

5.  The symbol for a degree is °.
 An angle measurement of 10 degrees is
written 10°.
 To measure an angle you have to use a
protractor.
 A protractor is a tool shaped like half a
circle with markings from 0° to 180°.

6. You need to make sure the protractor is lined up correctly.
Is this ready to measure the angle?

7. Look for the upside down ‘T’ in the middle of
the straight line on your protractor.
This needs to be exactly on the vertex of
your angle.

8. We need to remember.....
It doesn’t
matter which
way round the
angle is, you
ALWAYS need
to line the upside
down ‘T’ to the vertex
of the angle.

9. Read from the 0°, and follow the inner set of
numbers.

10. You then need to look at the 1° markings on
the outer set of numbers.

11. This angle measures 35°.

12.  Turn to page 15 in your textbook.
 Measure angle a.
 What did you get?

13.  You can classify an angle using its
measure.
 An acute angle is an angle whose
measure is greater than 0 and less than
90°.

15.  A right angle is an angle whose measure
= 90°.

17.  An obtuse angle is an angle whose
measure is greater than 90° and less than
180°.

19.  A straight angle is an angle whose
measure = 180°.

20.  Look again at the right angles.
 Lines that form right angles are said to be
perpendicular lines.
 The symbol for perpendicular lines is
 What 2 lines are
perpendicular?

21.  Complete pages 18-19 All
 You have 15 minutes.
 Homework: Workbook 5… You need a
protractor!!