Definition of Diagonal Line
The line joining any two non-adjacent 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 non-adjacent 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.
Correct Answer: A
Step 1: A regular hexagon has all of its sides and angles congruent.
Step 2: Draw the diagonals in a regular hexagon.
Step 3: 9 diagonals are formed joining the non-adjacent vertices.
Step 4: So, there are 9 diagonals in a regular hexagon.