棱长a正方体,表面积 6a^2,体积 a^3；球体直径D,表面积 πD^2；体积 πD^3/6；令：6a^2 = πD^2,a^2 :D^2 = π :6a :D = √π :√6D = a√(6/π)正方形体积：球体积=a^3：πD^3/6=a^3：π（a√(6/π)）^3/6=1：π（√...