Make five different quadrilaterals on a nine-point pegboard, without using the centre peg.
Work out the angles in each quadrilateral you make.
Perhaps checking that the four angles do add up to $360^\circ$!
Now, what other relationships you can see?
For printable sets of circle templates for use with this activity, please see Printable Resources page
Many thanks to Geoff Faux who introduced us to the merits of the 9 pin circular geo-board.