the dispersion relation for surface gravity waves on water of uniform depth h can be written, in the usual notation, as @2 = gktanh kh. From this result, show that the group speed do - 1 w khsech kh Co = 1 + 1 w + 2kh dk 2 k tanh kh 2 k sinh 2kh = 1 2kh 2 + sinh 2kh and hence show that Co