This chapter is based on polygons. We had published lecture notes on Polygons for Class 8 students. It would be a good idea to revise the Class 8: Polygons – Lecture Notes.

Important points to remember:

1. The sum of the interior angles of a convex polygon of $n$ sides is $(2n-4)$ right angles or $(2n-4) \times 90^o$.
2. If there is a regular polygon of $n$ sides $(n \ge 3)$, then each of its interior angle is equal to $\frac{2n-4}{n}$ $\times 90^o$
3. Each exterior angle of a regular polygon of $n$ sides is equal to $($ $\frac{360}{n}$ $)^o$
4. If each exterior angle of a regular polygon is $x^o$, then the number of sides in the polygon is $\frac{360}{x}$
5. As the number of sides of a regular polygon increase , the measure of each interior angle also increases.
6. If the polygon has $n$ sides, then the number of diagonals in $\frac{n(n-3)}{2}$.
7. The sum of all exterior angles formed by producing the sides of a convex polygon in the same order is equal to four right angles (or $360^o$).

All the problems related to Polygons can be solved using the above key formulas / points.