Circular measure — practice question

The figure shows $OAXB$ as a sector of a circle centred at $O$ with radius $10\,\text{cm}$. The chord $AB$ has length $12\,\text{cm}$. Line $OX$ passes through $M$, the midpoint of $AB$, and $OX$ is perpendicular to $AB$. The shaded part is enclosed by the chord $AB$ and the arc of a circle centred at $X$ with radius $XA$.