A typo in equation (6.24).

For $\zeta <1$, the corresponding equation should be:

$y(t)=k(1-e^{-\zeta {\omega }_{0}t}\cos {\omega }_{d}t-\frac{\zeta }{\sqrt{1-{\zeta }^2}}{e}^{-\zeta {\omega }_{0}t}\sin {\omega }_{d}t)$.

--Shuo