We will learn about the different terms related to polygons. We know, a polygon is a simple closed figure, bounded by straight line segment.

Sides of the polygon: The line segments forming a polygon are called its sides. The sides of the given polygons are AB, BC, CD, DE and EA.

Observe the sides AB and BC.

AB has an end point B and BC has an end point B, i.e., AB and BC have a common end point B. We call AB and BC adjacent sides of the polygon.

Thus, any two sides of a polygon having a
common end point are called adjacent sides.

The other pairs of adjacent sides of the polygon are BC and CD; CD and DE; DE and EA and EA and AB.

Vertices of the polygon: The point of intersection of two adjacent sides of a polygon is called its vertex (plural = vertices).

In the figure, sides EA and AB meet at A, hence A is a vertex of the polygon.

Similarly, B, C, D and E are other vertices of the polygon.

Observe the vertices A and B.

We see that they are the end points of side AB. These are called adjacent vertices.

Thus, the end points of the same side of a polygon are called adjacent vertices.

The other pair of adjacent vertices of the polygon are B and C; C and D; D and E; and E and A.

Diagonals of the polygon: Take any two vertices of the polygon which are not adjacent and join them. The line segment thus obtained is called the diagonal of the polygon.

Thus, if two vertices of a polygon which are not adjacent, the line segment so formed is called a diagonal of a polygon.

The diagonals of the polygon are AC, AD, BE, BD, and CE.

**● **Polygons

Polygon and its Classification

Interior and Exterior of the Polygon

Number of Triangles Contained in a Polygon

Angle Sum Property of a Polygon

Problems on Angle Sum Property of a Polygon

Sum of the Interior Angles of a Polygon

Sum of the Exterior Angles of a Polygon

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