# Area of a sector

**Geometry**Level pending

\(\Gamma\) is a circle with center \(O\). \(A\) and \(B\) are points on \(\Gamma\) such that the sector \(AOB\) has a perimeter of \(40\). Amongst all circular sectors with a perimeter of \(40\), what is the central measure of \(\angle AOB\) (in radians) of the sector with the largest area?

**Details and assumptions**

A central angle is an angle whose vertex is the center of a circle, and whose sides pass through a pair of points on the circle.