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Starter Questions

Starter Questions. B. 5. C. A. 12. 27 o. 1. Angles in a Semi Circle. Learning Intention. To investigate the special angle in a semi-circle. Angles in a Semi Circle. Tool-kit required. 1. Protractor. 2. Pencil. 3. Ruler. 3. You should have something like this.

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Starter Questions

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

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

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

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

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

  6. Log your results in a table. Outside Circumference Inside Angles in a Semi Circle 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 6

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

  8. B A C Angles in a Semi-Circle KeyPoint for 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 180o

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

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

  11. Example of Good Work Exercise Number Date 2 columns

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

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