To find the sum of the interior angles of a polygon, you can use the formula:
\[ \text{Sum of interior angles} = (n - 2) \times 180^\circ \]
where \( n \) is the number of sides of the polygon.
For a polygon with 9 sides:
\[ n = 9 \]
Now, substitute \( n \) into the formula:
\[ \text{Sum of interior angles} = (9 - 2) \times 180^\circ = 7 \times 180^\circ = 1260^\circ \]
Therefore, the sum of the interior angles of a 9-sided polygon is \( 1260^\circ \).