In the diagram, \(AB = AC = 8 \text{ cm}\) and angle \(CAB = \frac{2}{7} \pi\) radians. The circular arc \(BC\) has centre \(A\), the circular arc \(CD\) has centre \(B\) and \(ABD\) is a straight line.

(i) Show that angle \(CBD = \frac{9}{14} \pi\) radians.

(ii) Find the perimeter of the shaded region.