The sum of all the eight interior angles of a regular octagon is first obtained using the general formula:
[tex](n-2)\times180^o[/tex]where n = number of sides of the regular polygon
For a regular octagon, n = 8, and so we have:
[tex](8-2)\times180^o[/tex][tex]6\times180^o[/tex][tex]1080^o[/tex]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:
[tex]\frac{1080^{o^{}}}{n}[/tex][tex]\frac{1080^o}{8}=135^o[/tex]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:
[tex]\text{Sum of 7 interior angles = 7}\times135=945^o[/tex]Therefore, the sum of 7 of the interior angles of a regular octagon is 945 degrees