文[1]探究了海伦公式的推广问题.由于三角形被三条边长完全确定,而四边形则否,因此,作者认识到与海伦公式不同,四边形的面积不能用四边长通过一个式子表示.接下来,作者考虑了几种特殊情况,根据四边形有外接圆、四边形有内切圆、四边形既有外接圆又有内切圆等不同情况,给出了只 [1] explored the problem of generalization of the Helen formula. Since the triangle is completely defined by the three sides and the quadrangle is not, the author recognizes that, unlike the Helen formula, the area of ​​the quadrilateral can not be represented by an equation of length. Down, the author considered several special cases, according to the circumscribed circle quadrilateral, quadrilateral inscribed circle, quadrilateral circumscribed circles have both circumscribed circles and other different situations given only