1. The problem is to find the formula for the number of interior angles of a polygon. 2. A polygon with $n$ sides has $n$ interior angles. 3. The sum of the measures of the interior angles of a polygon with $n$ sides is given by the formula: $$\text{Sum of interior angles} = (n-2) \times 180$$ 4. Each interior angle (if the polygon is regular) can be found by dividing the sum by $n$: $$\text{Each interior angle} = \frac{(n-2) \times 180}{n}$$ 5. Important rules: - The polygon must have at least 3 sides ($n \geq 3$). - The formula calculates the sum of all interior angles. - For regular polygons, all interior angles are equal. 6. To summarize: - Number of interior angles = $n$ - Sum of interior angles = $(n-2) \times 180$ - Each interior angle (regular polygon) = $\frac{(n-2) \times 180}{n}$ This completes the explanation of the formula for the number of interior angles and their measures.