Chord-Centre Theorem

Circles are everywhere in real life — the rim of a bicycle wheel, the arch of a bridge, the plan of a circular paddy plot being surveyed. When engineers hold up a dome or a surveyor finds the exact centre of a round piece of land, they lean on a small set of facts about how a straight chord sits inside a circle and how angles open up across it. In this lesson you learn those facts, and you will use them — together with Pythagoras — right through your O/L geometry paper.