To find the sum of the interior angles of a hendecagon (an 11-sided polygon), you can use the formula:
\[ \text{Sum of interior angles} = (n - 2) \times 180^\circ \]
where \( n \) is the number of sides in the polygon.
For a hendecagon, \( n = 11 \):
\[ \text{Sum of interior angles} = (11 - 2) \times 180^\circ = 9 \times 180^\circ = 1620^\circ \]
So, the sum of the interior angles of a hendecagon is \( 1620^\circ \).