Circle Formulas

Angles

100

Central angle

angle = arc

200

Inscribed Angle

angle = 1/2 arc

300

Angle in a circle

angle = 1/2(arc + arc)

400

Angle outside of a circle

angle = 1/2(far arc - close arc)

Theorems

100

Tangent-Tangent Theorem

tangent = tangent

200

Chord-Chord theorem

part x part=part x part

300

Secant-Secant theorem

outside x whole=outside x whole

400

Secant-Tangent theorem

outside x whole=outside^2

Other

100

area

A = pi.r^2

200

Circumference

C = pi. x d =2pi.r

300

arc length

l = x/360* x 2pi.r

400

area of a sector

A = x/360* x pi.r^2

500

equation of a circle

(x - h)^2 + (y - k)^2 = r^2