8,9

Find the sum of the exterior angles of a convex $n$-gon, taken one at each vertex.
The sum of the interior angles of a convex $n$-gon is $180^{\circ}(n-2)$.

## Solution

The sum of the straight angles at all vertices of the $n$-gon is $180^{\circ} n$. The sum of the interior angles of a convex $n$-gon is $180^{\circ}(n-2)$. The sum of the exterior angles of this $n$-gon is the difference between these sums, which is $360^{\circ}$.

## Answer

$360^{\circ}$.