The formula for the sum S of interior angles of a polygon is:
S = (n - 2) * 180º
where n is the number of sides of the polygon.
Thus, since an octagon has 8 sides, the sum of the measures of the interior angles is:
S = (8 - 2) * 180º = 6 * 180º = 1080º
Therefore, the third option is correct.
