Question

The number of diagonals that can be drawn in a hexagon is

Answer 1

A hexagon has $6$ sides. We obtain the diagonals by joining the vertices in pairs.
Total number of sides and diagonals $={}^6{C}_2=\frac{6\times 5}{2\times 1}=5\times 3=15$
This includes its $6$ sides also.

Hence, the number of diagonals is $15-6=9.$