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'Right Angles' printed from http://nrich.maths.org/
Can you make a right-angled triangle on this peg-board by joining
up three points round the edge?
Can you work systematically to prove this?
This text is usually replaced by the Flash movie.
Now try changing the number of points round the edge.
Can you do it now?
Can you show by calculation that the angle is a right angle?
What do you notice about the side of the triangle opposite the
Try this with other numbers of points round the edge.
When is it possible to make a right-angled triangle?
In this interactivity, the points are equally spaced around a
circle. Imagine that they are not.
Can you explain the conditions which will give a right-angled
Can you prove this?
Many thanks to Geoff Faux who introduced
us to the merits of the 9 pin circular geo-board.
The boards, moulded in crystal clear ABS
that can be used on an OHP (185 cm in diameter), together with a
teacher's guide, are available from Geoff at Education