NIELIT 2017 July Scientist B (IT) - Section B: 15

Question

The number of diagonals that can be drawn by joining the vertices of an octagon is

• A. $28$
• B. $48$
• C. $20$
• D. None of the option

Answer 1

A diagonal is a line segment joining two vertices whereas those vertices are not sharing the same edge.

Therefore,

The number of diagonals that can be drawn by joining ‘n’ vertices =  (Total edges possible) – n

                                                                                                                     = C(n,2) – n

So for octagon the no. of diagonals possible = 20

(C) is the answer