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1 Starter Questions Starter Questions A B C 5 12 27 o.

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Presentation on theme: "1 Starter Questions Starter Questions A B C 5 12 27 o."— Presentation transcript:

1 1 Starter Questions Starter Questions A B C 5 12 27 o

2 Learning Intention To investigate the special angle in a semi-circle. Angles in a Semi Circle

3 3 Tool-kit required 1.Protractor 2.Pencil 3.Ruler Angles in a Semi Circle

4 4 1.Using your pencil trace round the protractor so that you have semi-circle. 2.Mark the centre of the semi-circle. You should have something like this. Angles in a Semi Circle

5 Mark three points 1. Outside the circle x x x x x x x x x 2. On the circumference 3. Inside the circle Angles in a Semi Circle

6 6 For each of the points Form a triangle by drawing a line from each end of the diameter to the point. Measure the angle at the various points. x x x Log your results in a table. InsideCircumferenceOutside Angles in a Semi Circle

7 7 Inside Circumference Outside x x x < 90 o > 90 o = 90 o Online Demo Angles in a Semi Circle

8 KeyPoint for Angles in a Semi-circle Angles in a Semi-Circle A triangle ABC within a semicircle with base the length of the diameter will ALWAYS be right angled at P on the circumference. Remember - Angles in any triangle sum to 180 o B AC

9 9 Hints Example 1 : Sketch diagram and find all the missing angles. 70 o Look for right angle triangles 43 o 20 o 47 o Remember ! Angles in any triangle sum to 180 o Angles in a Semi-Circle

10 Example 2 : Sketch the diagram. Angles in a Semi-Circle C AB D 25 o 60 o (a)Right down two right angle triangles (a)Calculate all missing angles. E

11 2 columns Date Exercise Number Example of Good Work

12 Now try Ex 2 Ch12 (page 138) Sketch shapes Angles in a Semi-Circle


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