3.23: Tangents meeting outside a circle

The diagram shows a circle, centre $O$, radius $10\text{ cm}$. The points $A$ and $B$ lie on the circumference of the circle. The tangent at $A$ and the tangent at $B$ meet at the point $C$. The angle $AOB$ is $\theta$ radians. The length of the minor arc $AB$ is $28\text{ cm}$.