## Circles

### Definitions

- Arc
- Chord

### Formulae

Circumference

area

^{2}

Remember from

### Circles

tangents, angles subtended cyclic quadrilaterals area of circle, area of triangle congruent similar

### Angles Subtended inside a Circle

Consider an arc (or alternatively a chord) The angle subtended at the circumference by this arc is half the anglr that would be subtended by the arc at the center of the circle