Notes on Understanding Quadrilaterals
Introduction
Polygon – Polygon is a combination of two Greek words Polus + Gonia, in which Polus means many and
Gonia means Corner or angle.
Classification of Polygons
Polygons are classified as per their sides or vertices they have.
(a) Triangle – A triangle has three sides and three vertices.
b) Quadrilateral – A quadrilateral has four sides and consecutively four vertices.
(c) Pentagon – (Penta means five) A pentagon has five sides and five vertices.
(d) Hexagon – (Hexa means six) A hexagon has six sides and six vertices.
(e) Heptagon – (Hepta means seven) A heptagon has seven sides and seven vertices.
(f) Octagon – (Octa means eight) A octagon has eight sides and eight vertices.
(g) Nonagon – (Nona means nine) A nonagon has nine sides and nine vertices.
(h) Decagon – (Deca means ten) A decagon has ten sides and ten vertices.
Diagonals
A line segments which connects two non-consecutive vertices of a polygon is called diagonal.
Quadrilateral
This is the combination of two Latin words; Quardi + Latus. Quadri – means four and Latus means side.
Hence, a polygon with four sides is called quadrilateral. In quadrilateral, sides are straight and are of two
dimensional. Square, rectangle, rhombus, parallelogram, etc. are the examples of quadrilateral.
Angle sum of a polygon = (n – 2) x 180⁰
Where ‘n’ is the number of sides
Example:
A triangle has three sides,
Thus, Angle sum of a triangle = (3 – 2) x 180⁰ = 1 x 180⁰ = 180⁰