Angles - July 2005, Stage 3&4

Problems

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Triangles in Circles

Stage: 3 Challenge Level: Challenge Level:1

How many different triangles can you make which consist of the centre point and two of the points on the edge? Can you work out each of their angles?

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Subtended Angles

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

What is the relationship between the angle at the centre and the angles at the circumference, for angles which stand on the same arc? Can you prove it?

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Right Angles

Stage: 3 and 4 Challenge Level: Challenge Level:2 Challenge Level:2

Can you make a right-angled triangle on this peg-board by joining up three points round the edge?

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Pegboard Quads

Stage: 4 Challenge Level: Challenge Level:1

Make five different quadrilaterals on a nine-point pegboard, without using the centre peg. Work out the angles in each quadrilateral you make. Now, what other relationships you can see?

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Sine and Cosine for Connected Angles

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

The length AM can be calculated using trigonometry in two different ways. Create this pair of equivalent calculations for different peg boards, notice a general result, and account for it.

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Figure of Eight

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

On a nine-point pegboard a band is stretched over 4 pegs in a "figure of 8" arrangement. How many different "figure of 8" arrangements can be made ?