Circles


Definitions

  • Arc
  • Chord

Formulae

Circumference

π d

2 π r

area

π r2

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