9. (6 points) In isosceles $\triangle A B C$, the ratio of the measures of two interior angles is 1:2. Then, the largest angle in $\triangle A B C$ can be $\qquad$ degrees.
【Solution】Solution: $180^{\circ} \times \frac{2}{1+1+2}$
$$
\begin{array}{l}
=180^{\circ} \times \frac{1}{2} \\
=90^{\circ}
\end{array}
$$

Answer: The maximum angle can be 90 degrees. Therefore, the answer is: 90.