In reply to @DavidKButlerUoA
@DavidKButlerUoA @icecolbeveridge They're def circular arcs. I *think* they're at right angles, would need to do some working out to show it
In reply to @christianp
@DavidKButlerUoA @icecolbeveridge yes, of course they are: the centre of the circle lies on both lines formed by extending the edges