Question:
Tick (✓) the correct answer:
How many diagonals are there in a hexagon?
(a) 6
(b) 8
(c) 9
(d) 10
Solution:
(c) 9
Number of diagonals in an $\mathrm{n}$-sided polygon $=\frac{n(n-3)}{2}$
For a hexagon:
$n=6$
$\therefore \frac{n(n-3)}{2}=\frac{6(6-3)}{2}$
$=\frac{18}{2}=9$