CBSE Class 8 Answered

Consider the following polygon.

Through a single vertex of a polygon, draw all possible diagonals.

Here, the number of sides of a polygon = 5 = n

And, the number of triangles formed = 3 = n - 2

That is, if the number of sides of a polygon is n, the number of triangles formed will be (n - 2).

The sum of the angles of a triangle = 180 degrees

Then, the sum of the angles of (n - 2) triangles = (n - 2) x 180 degrees

Hence, the sum of interior angles of a polygon with n sides = (n - 2) x 180 degrees