Question

How many diagonals can be drawn by joining the angular points of polygon of 12 sides?

Answer 1

Answer:

polygon of 12 sides has 12 vertices

so no of ways to choose 2 points from 12 points =12 !12 12×11!10

C = ------------ = ---------------

2 !2 !12-2 1×2 !10

=66

but in it 12 are sides of polygon

so no of diagonals =66-12=54