KCET 2025 Math Paper

To find the number of diagonals in an octagon (a polygon with 8 sides), use the formula for the number of diagonals in a polygon, which is:
‌

n(n−3)

2

where n is the number of sides of the polygon.
For an octagon, n=8. Plug this value into the formula:
‌

8(8−3)

2

=‌

8×5

2

=‌

40

2

=20
Therefore, an octagon has 20 diagonals.