1. Angles in a straight line and around a point

2. Lesson Objectives To understand the sum of angles in a straight line
To understand the sum of angles around a point
To be able to answer questions by using these two rule to find unknown angles.

3. What angle is this?
=90°
A right-angle

4. If there are 90° in a right-angle, how many are their in a straight line?
90°+90°=
180°

5. As there are 180° in a straight line, what is the unknown angle here?
135°
45°
180°- 45° =
135°

6. If the angles in a straight line equal 180°, what do the angles around a point add up to?
90°
90°
90°
90°
90°+90°+90°+90°=
360°

7. As there are 360° around a point, what is the unknown angle here?
45°
45°
100° ?
110°
360° - 45° - 60° - 45° - 100° =
110°

8. Copy out the following definitions:
45° ?
180°- 45° =
135°
Angles in a straight line = 180°
45°
60°
100° ?
360° - 45° - 60° - 45° - 100° =
110°
Angles around a point = 360°

9. Plenary What are the missing angles?
57°
123° a
89° b
46°
45°

10. What are the missing angles?
150°
30° X Z
30° Y
150°