Circles

An arc is part of the circumference; a sector is a pie-slice of a circle. Both are calculated as a fraction of the full circle, where the fraction = angle ÷ 360.

Formulas for the area and circumference of a circle, and how to apply them.

The circumference is the distance around the outside of a circle. It equals π multiplied by the diameter, or 2π multiplied by the radius.