Long description
The figure consists of a circle and two joined line segments. The centre of the circle is marked with a solid dot. This point is labelled with its coordinates, open bracket, a comma b, close bracket. A vertical line segment extends upwards from the centre of the circle, reaching about two-thirds of the way to the circumference. A point half-way up the line segment is marked with a solid dot, and labelled with its coordinates, open bracket, a comma s, close bracket. Another point at the top end of the vertical line segment is also marked with a solid dot, and labelled with its coordinates, open bracket, a comma y, close bracket. From this point at the top of the vertical line segment, a horizontal line segment extends to the right, reaching close to the circumference but remaining inside the circle. Half-way along it, a point is marked with a solid dot, and labelled with coordinates, open bracket, r comma y, close bracket. At the right-hand end of the horizontal line segment, a point is marked with a solid dot, and labelled with coordinates, open bracket, x comma y, close bracket.