As per above table, convex polygon with 4 sides have angle sum (4-2) × 180° = 360°.
(a) (7-2) × 180° = 900° is the angle sum of convex polygon with 7 sides.
(b) (8-2) × 180° = 1080° is the angle sum of convex polygon with 8 sides.
(c) (10-2) × 180° = 1440° is the angle sum of convex polygon with 10 sides.
(d) For n sides (n-2) × 180° is the angle sum of convex polygon with n sides.