The sum of the interior angles of an n-sided polygon can be calculated using formula
[tex]\Sigma =(n-2)\cdot 180^{\circ}.[/tex]
It is easy to verify:
1. If n=3 (the smallest possible number of sides for polygon), then the polygon is triangle and the sum of the measures of interior angles of triangle is always 180° .
2. If n>3, draw (n-3) diagonals from one vertex. This diagonals partition the polygon into (n-2) triangles. Thus, the sum of the interior angles of an n-sided polygon is equal to the sum of the measures of interior angles of (n-2) triangles that is
[tex]\Sigma =(n-2)\cdot 180^{\circ}.[/tex]
Answer: correct choice is B
