Portion of a
circle bounded by a
chord and the
arc subtended by the chord.
Formula

The area of a circular segment is given by the relationship :
A =
r[latex]^{2}[/latex][[latex]\frac{α}{2}[/latex] – [latex]\frac{1}{2}\small\sin(α)[/latex]], where
α is the measure in radians of the angle at the centre.
Example
The shaded portion of the figure is a circular segment :