Circle formulas

Central angle

Central angle

Arc length=measure

Inscribed angles

Arc length/2

Overlapping arcs

m<ABD=m<ACD

Inscribed Quadrilaterals

Opposite angles are supplementary

Intersecting chords or secant on the interior

m<1=(AB)+(CD)/2
m<2=(AC)+(BD)/2

Intersecting tangents and chords/secants on the circle

m<1= major arc/2
m<2=minor arc/2

Intersecting secants on the exterior

big arc-small arc/2

Intersecting secants and tangents on the exterior

big arc-small arc/2

Intersecting Tangents on the exterior

Big arc-small arc/2

Tangents

Line AB is perpendicular to Segment CD

Two tangents from the same external point

The two tangents are congruent

Intersecting chords or secants on the interior

part of chord*other part=part of chord*other part

Intersecting secants on the exterior

outside*whole=outside*whole

Intersecting tanget and secant on the exterior

tangent²=outside*whole

Area

A= πr²

Circumference

C = 2πr
C = πd

Arc Length

l= x*2πr/360

Standard Equation of a Circle

(x-h)²+(y-k)²=r²

Sector area

angle measure/360*πr²