Explanation

The sum of the internal angles of a polygon can be found using the formula:

(n-2) × 180°

where n is the number of sides.

For a regular octagon (8 sides):

(8-2) × 180° = 6 × 180° = 1080°

Since it's a regular octagon, all internal angles are equal. To find the measure of each internal angle, divide the total sum by the number of angles:

1080° ÷ 8 = 135°