Question

The expression for the number of diagonals that we can make from one vertex of a n-sided polygon is

Answer 1

Since a vertex is formed by joining two sides. Diagonal is line segment joinging the two opposite vertex. So, the number of diagonal formed by one vertex = n - 3 (minus three because two points adjacent to it and the one itself is excluded).
Thus, the number of diagonals will be n - 3.