Solution
= Solution
Set
$$
A=\sqrt{\frac{2T}{I_2}},
\qquad
\Omega=A\sqrt{\frac{I_2-I_1}{I_2+I_1}}
=\sqrt{\frac{2T(I_2-I_1)}{I_2(I_1+I_2)}}.
$$
Then $\omega_1=A\operatorname{sech}(\Omega t)$ satisfies the squared equation and the stated initial condition after choosing the origin of time at the maximum of $\omega_1$.