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UNDERSTANDINg QUADRIlATERAlS

Curves Polygons Quadrilaterals

A figure which is drawn A polygon is a simple closed curve Any 4-sided polygon is called a
without lifting the pencil formed by only line segments. quadrilateral.
from the paper and without
retracing any portion of Number Polygon Sample
the drawing. of sides example figure
3 Triangle
A curve that does not begin 4 Quadrilateral Kinds of Quadrilaterals
and end at the same point
is called an open curve. 5 Pentagon Quadrilaterals are classified into

6 Hexagon three categories: Trapezium, Kites
and Parallelograms.
7 Heptagon
A curve that begins and
ends at the same point is 8 Octagon
called a closed curve.
9 Nonagon
10 Decagon

Classification of Polygons

Regular Irregular Convex Concave Simple

Properties of Polygon Construction of Quadrilaterals
l The number of diagonals of a polygon are We can construct a unique quadrilateral when the following
(
nn − ) 3 measurements are given:
calculated by using the formula ,
2 (a) When the measures of 4 sides and 1 diagonal are given.
where n is the number of sides of the polygon. (b) When the measures of 3 sides and 2 diagonals are given.
l The sum of interior angles of a polygon = (c) When the measures of 3 sides and 2 included angles are
(n – 2) × 180°, where n = number of sides of given.
the polygon. (d) When the measures of 4 sides and 1 angle are given.
l For a regular polygon of n sides, the measure (e) When the measures of 2 adjacent sides and 3 angles are
360° given.
of each exterior angle will be .
n (f) When other special properties are known.

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