Answer
$(0,\infty)$
Work Step by Step
$y''+cos(t)y'+3ln|t|y=0$
To use Theorem 3.2.1:
$p(t)=cos(t)$ which is continuous on $(-\infty,\infty) $
$q(t)=3ln|t|$ which is continuous on $(0,\infty) $
$g(t)=0$ which is continuous on $(-\infty,\infty) $
Thus, $p(t),q(t),$ and $g(t)$ are all continuous on $(0,\infty) $
Since $t_0=2$, the solution exists on $(0,\infty) $