In a regular octagon all the interior angles are of the same value. sum of the interior angles in octagon = (n-2) *180° n - number of sides, in this case, n = 8 interior angles sum = (8-2)*180° = 6*180° = 1080° since there are 8 equal angles = 1080/8 = 135° Angle x + one interior angle of the octagon = 180 ° (as its a straight line) x + 135 = 180 x = 45°
