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Angles in a straight line and around a point. Lesson Objectives To understand the sum of angles in a straight line To understand the sum of angles around.

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Presentation on theme: "Angles in a straight line and around a point. Lesson Objectives To understand the sum of angles in a straight line To understand the sum of angles around."— Presentation transcript:

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°+90°=180°

5 As there are 180° in a straight line, what is the unknown angle here? 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°=360°

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

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

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

10 What are the missing angles? 150° X Y Z30° 150° 30°


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