How can we help?

You can also find more resources in our Help Center.

Area of a Circle

πr²

Circumference of a Circle

2πr or πd

Measure of an Angle on a Circle

½(measure of intercepted arc)

Measure of an Angle inside a Circle

½(measure of intercepted arc + measure of vertical angle's intercepted arc)

Measure of an Angle outside a Circle

½(measure of large intercepted arc - measure of small intercepted arc)