Solution
= Solution
Put $T=\pi/\omega$, $t_0=T/2$, and $\Omega=\omega/2$. A solution satisfying both endpoint conditions is
$$
y=Ae^{-\gamma t/2}\sin(\Omega t)+\frac I\Omega e^{-\gamma(t-t_0)/2}\sin(\Omega(t-t_0))H(t-t_0),
$$
where $A=-\sqrt2I\omega^{-1}e^{\sqrt3\pi/4}$. The <derivative> jumps by $I$ at $t_0$, as required.