Page 158 - Maths Skills - 8

156 Maths

Classification of Polygons
No. of sides Classification Sum of No. of sides Classification Sum of
or vertices interior angles or vertices interior angles

I 900°

3 I II
180° 7 III
Triangle IV V (5 × 180°)
Heptagon

I II 1,080°
I 360°
III
II 8 IV
4 V
Quadrilateral VI (6 × 180°)

(2 × 180°) Octagon

I
II 1,260°
I 540° III
IV
II 9 V
5 III VI
VII
Pentagon Nonagon (7 × 180°)
(3 × 180°)

I
II II III 1,440°
I IV 720°
III 10 IV V
6
Hexagon VI VII
(4 × 180°) VIII (8 × 180°)
Decagon

Diagonals of a Polygon
A diagonal is a line segment connecting two non-consecutive vertices of a polygon. In a triangle, a diagonal is not
possible, thus the concept of diagonal starts from quadrilateral onwards as shown below.

Polygon No. of Sides Number of Diagonals

D
A
4 2 (AC and BD)

B C