1. What are the polygons?
A polygon is a 2D shape with three or more straight sides. Triangles are polygons with three sides, quadrilaterals are polygons with four sides.
For example,
1.1 Types of polygons
There are two types of polygons:
[A] Regular polygons: Regular polygons have equal sides and equal interior angles.
Example:
[B] Irregular Polygons: Irregular polygons have different sides and angles.
Examples:
1.2 Diagonals of Polygon
A diagonal of a polygon is a line which joins two non-neighbouring corners. For example, the diagonals for a quadrilateral and a
Formula:
Number of diagonals for an n-sided polygon = n(n - 3) ÷ 2
1.3 Interior and Exterior Angles of polygons
Interior angles are angles formed inside a polygon. Exterior angles are angles formed outside the polygon by extending one side of the polygon.
For example,
The formula to find the interior and exterior angles of the n-sided polygon (regular or irregular):
Sum of interior angles = (n - 2) × 180°
Interior angle = 180° - Exterior angle
Exterior angle = 360° ÷ n
Interior angle = (n-2) × 180° ÷ n
