Formulas for circles chapter 8

Area of a circle

Area of a circle

A=πr² or A = pi r²

Annulus of a circle

Are of annulus of a circle = area of a big circle-area of the smaller circle

π(R²-r²)

Sector of a circle

Area of sector = degrees/360 •pi r²

Sector Area = (θ/360°) × πr²

Circumstances of a circle formula

C=2•pi•r or C= pi•d

C=2πr or C=πd

Arc length of a circle

Arc length = degree of measure of arc / 360 • 2 •pi•r

s = 2 π r (θ/360°)

Equations of a circle

(X-h)²+(y-k)² =r²