Notes of polygon and all formula of class 8 full notes with best explanation

Notes of polygon (best explanation)

A plane shape (two-dimensional) with straight sides.

Examples: triangles, rectangles and pentagons.

(Note: a circle is not a polygon because it has a curved side)

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an area enclosed by line segments only is called polygon

Types of polygons:

On basis of sides ,POLYGONS are of two types

1.REGULAR POLYGONS

2.IRREGULAR POLYGONS

1.Regular polygon:     a polygon is said to be regular if its all sides are equal

2.Irregular polygons: a polygon is said to be irregular if its all sides are not equal

please note that the names of polygons are bases on the number of sides present in them

examples of polygons:-

polygons                                                              number of sides

1.triangle                                                              3 sides

2.quadrilateral                                                      4 sides

3.pentagon                                       5 sides

4.hexagon                                                               6 sides

5.heptagon                                                             7 sides

6.octagon                                                                8 sides

7.nonagon                                                                9 sides

8.decagon                                                                10 sides

If all sides of triangle are equal then it is called Equilateral triangle
If all sides of quadrilateral are equal then it is called  Square 

On the basis of Angles :-

Polygons are of two types:

1.Concave polygon:     Polygons having at least one interior angle more than 180 degree are called Concave polygons

2.Convex polygon:   Polygons having each interior angle less than 180 degree are called  Convex Polygons

• The sum of all the exterior angles = 360°
• Interior angle + corresponding exterior angle = 180°.
• The sum of the interior angles of a convex POLYGON, having n sides is 180° (n - 2).
• The sum of the exterior angles of a convex polygon, taken one at each vertex, is 360°.

• The measure of an exterior angle of a regular n- sided polygon is 
• The measure of the interior angle of a regular n-sided polygon is 
• The number of diagonals of in an n-sided polygon is 

Perimeter of a polygon: The perimeter of a polygon is the sum of the lengths of all its sides.

Area of a polygon: The region enclosed within a figure is called its area.

Diagonal of a polygon: The segment joining any two non-consecutive vertices is called a diagonal.

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