Polygon: Polygon is a combination of two Greek words Polus + Gonia, in which Polus means many and Gonia means Corner or angle. Thus, a plane figure bounded by a finite straight line segment in loop to form a closed chain is called a polygon.
Polygons are classified as per their sides or vertices they have.
(a) Triangle: A triangle has three sides and three vertices.
(b) Quardilateral: A quardilateral has four sides and consequetively 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.
x(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.
(.) n – gon: A n-gon has n sides and n vertices. (Where n = 3, 4, 5, 6, ……..)
A line segments which connects two non-consecutive vertices of a polygon is called diagonal.
An equilateral and equiangular polygon is called regular polygon. This means if a polygon has all angles equal and all sides equal is called regular polygon. For example – An equilateral triangle has all angles and sides equal, and hence is an regular polygon, A square is also a regular polygon.
Polygon which has equal angles but not equal sides is called irregular polygon. For example – a rectangle has equal angles but not equal sides, and hence an irregular polygon.
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, rhombous, parellelogram, etc. are the examples of quadrilateral.
Angle sum of a polygon `= (n – 2) xx 180⁰`
Where ‘n’ is the number os sides
A triangle has three sides,
Thus, Angle sum of a triangle `= (3 – 2) xx 180⁰ = 1 xx 180⁰ = 180⁰`
A quadrilateral has four sides,
Thus, Angle sum of a quadrilateral `= (4 – 2) xx 180⁰ = 2 xx 180⁰ = 360⁰`
A pentagon has five sides,
Thus, Angle sum of a pentagon `= (5 – 2) xx 180⁰ = 3 xx 180⁰ = 540⁰`
Similarly, angle sum of any polygon can be calculated.
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