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'Triangles in Circles' printed from http://nrich.maths.org/

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In this problem you can make use of the coloured rubber bands in the interactivity below.

How many different triangles can you make which consist of the centre point and two of the points on the edge?

Can you find the angle at the centre point each time?

Can you find the other two angles in each triangle?

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If you'd like to work on paper, you could use a print out of these nine-peg circles .


Look at these two triangles. Can you work out each of their angles?

Two triangles on the Geoboard

Draw some other triangles on the 9 peg circles. Can you work out each of their angles?

Many thanks to Geoff Faux who introduced us to the merits of the 9 pin circular geo-board.