The diagram shows triangle ABC which is right-angled at A. Angle ABC = \frac{1}{5}\pi radians and AC = 8 cm. The points D and E lie on BC and BA respectively. The sector ADE is part of a circle with centre A and is such that BDC is the tangent to the arc DE at D.

(i) Find the length of AD.

(ii) Find the area of the shaded region.