The **sector area** is the measure of the area along the curved line filling up the arc sector. It is longer than the straight line distance between its endpoints (which would be a chord)
The formula the arc measure is:

where:

- is the central angle of the arc in degrees
*R*is the radius of the arc

Recall that is the area of the whole circle, so the formula simply reduces this by the ratio of the arc angle to a full angle (360). By transposing the above formula, you solve for the radius, central angle, or secto area if you know any two of them.

The sector area of a Polygon is:

## Circumscribed sector area

The sector area of a circumscribed circle is:

## Inscribed sector area

The sector area of a inscribed circle is: