An octagon has eight sides and eight interior angles, in a regular octagon the sides and angles are all equal and the sum of all the interior angles is 360 degrees. If there are eight angles and the sum of the angles is 360 degrees then one angle is equal to 360/8 or 45 degrees, your answer

The formula to find exterior angle of a regular polygon is given by 360/n where n is the number of sides. Here as n=8, therefore the ext. Angle is given by 360/8 = 45 degrees

S=(N-2)180

I think both sides are 221/2 Deg.