Diagonal Line
Definition of Diagonal Line
The line joining any two nonadjacent vertices of a polygon is called diagonal line.
More About Diagonal Line

The number of diagonals of a polygon can be calculated using the formula d = ,
where S is the number of sides in the polygon.
The number of diagonals in a polygon with 5 sides = = 5.
Example of Diagonal Line

In the given figure, A and C, B and D are the nonadjacent vertices.
The line joining any of these pairs of vertices is called diagonal of the figure.
So, AC and BD are the diagonals of the given figure.
Video Examples: How to Find the Length of a Diagonal Line Running Though a Rectangle : Math Tips
Solved Example on Diagonal Line
Ques: Find the number of diagonals in a regular hexagon.
Choices:
A. 9B. 6
C. 12
D. 3
Correct Answer: A
Solution:

Step 1: A regular hexagon has all of its sides and angles congruent.
Step 2: Draw the diagonals in a regular hexagon.
Step 4: So, there are 9 diagonals in a regular hexagon.
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