Answer: Use this formula
Area = (number of sides × length of one side × apothem)
Step-by-step explanation: The formula to calculate the area of a regular polygon is, Area = (number of sides × length of one side × apothem)/2, where the value of apothem can be calculated using the formula, Apothem = [(length of one side)/{2 ×(tan(180/number of sides))}].