我们知道,四边形具有不稳定性.即使四条边的长度已知,也不能确定它的形状.相对于三角形的稳定性而言,四边形的这种不稳定性给我们的研究带来了很大的不便.也因此造成对四边形的研究成果很少,与三角形结论的极度丰富相比,关于四边形的结论相当匮乏.那么,如果已知某四边形的四条边长,需要附加什么条件才能够确定这个四边形?历史上,有许多人做过尝试(见文[1]),并得到了许多有意义的结论.这不仅是传统数学文化的宝贵资源,也是 We know that the quadrilateral is unstable, and its shape can not be determined even if the length of the four sides is known. The instability of the quadrilateral relative to the stability of the triangle brings a great Inconvenience.Therefore, the result of the research on the quadrilateral is very little, and the conclusion about the quadrilateral is rather scarce compared with the extreme enrichment of the triangle conclusion.Then, if we know the four sides of a quadrilateral, what conditions need to be added to determine the quadrilateral? Historically, there have been many attempts (see [1]) and many meaningful conclusions have been made, which is not only a valuable resource for traditional mathematical culture but also