Because the rectangular area πR? Because the infinitesimal sector carries the vacancy angle outside the arc, it is transformed into the tangent of the circle 6x2? The area of polygon must be greater than the area of circle; πr？ With the infinite division of the small fan, the umbrella between the arc and the chord will be lost, but it will be transformed into a circle inscribed with positive 6x2. The area of a polygon must be smaller than that of a circle. According to the axiom of area "softening" equal area deformation, it is found that if the circular area is 7a? So its circumscribed circle area is 9a? Therefore, it is introduced that "the circular area is equal to two thirds of the diameter d and seven times the square of 1".

Because the area of a circle is: s=7(d/3)? So the diameter of the circle is: d=3√s/7.