A regular polygon is centred at a point. Use the stepper to change the number of sides, or drag the rim handle to change its size. From the centre, the apothem is drawn perpendicular to one side, and a radius is drawn to a corner. The polygon's area equals one half times the apothem times the perimeter. The number of sides, side length, apothem, perimeter and area are shown live. As the number of sides grows, the polygon and its area approach the circle through the corners. An info button opens a drawer with the formula.