It’s no wonder that farmers with fields in the plains surrounding Stonehenge, in southern England, face late-summer mornings with dread. On any given day at the height of the growing season, as many ...

AO and OC are both radii of the circle. Length AO = Length OC Draw the line OB. It creates two triangles OCB and OAB. These share the length OB.

It is important to remember other angles rules, such as angles on a straight line add up to 180°, and to recognise angles in parallel lines. Make sure you are confident in applying Pythagoras’ theorem ...