The sum of all the eight interior angles of a regular octagon is first obtained using the general formula:
where n = number of sides of the regular polygon
For a regular octagon, n = 8, and so we have:
Now, we divide this total sum by the number of sides of the regular octagon in order to obtain the measure of an individual interior angle of the octagon, as follows:
Now, to find the sum of 7 interior angles of a regular octagon, we simply multiply an individual interior angle of the octagon by 7, as follows:
Therefore, the sum of 7 of the interior angles of a regular octagon is 945 degrees