Circles, arcs and sectors
Pages
Circumference of a circle
C = πd or 2πr, and deciding whether the given length is a radius or a diameter.
Area of a circle
A = πr² with only the radius squared.
Answers in terms of π
Leaving circle answers as exact multiples of π instead of decimals.
Semicircles and quarter circles
Halving or quartering the circle formulas.
Arc length
The angle over 360 as the fraction of the circumference an arc takes.
Area of a sector
The angle over 360 applied to πr² for the area a sector sweeps.
Finding the angle of a sector
Running the arc and sector formulas backwards to recover the angle or radius.
Practice
Circumference of a circle
C = πd or 2πr, and deciding whether the given length is a radius or a diameter.
PracticeArea of a circle
A = πr² with only the radius squared.
PracticeAnswers in terms of π
Leaving circle answers as exact multiples of π instead of decimals.
PracticeSemicircles and quarter circles
Halving or quartering the circle formulas.
PracticeArc length
The angle over 360 as the fraction of the circumference an arc takes.
PracticeArea of a sector
The angle over 360 applied to πr² for the area a sector sweeps.
PracticeFinding the angle of a sector
Running the arc and sector formulas backwards to recover the angle or radius.
PracticeArea, surface area and volume review
Circles, sectors, prisms, cones, spheres and frustums, exact in terms of π.