20 0 2年天津市中考试卷第一题的第 1 0小题为 :已知四边形ABCD的对角线AC与BD相交于点O ,若S△AOB =4 ,S△COD =9,则四边形ABCD的面积S四边形ABCD 的最小值为A 2 1　B 2 5　C 2 6　D 36图 1我们给出如下解法 ,对试题给出分析与评价 .解　如图 1 ,过点A、C作BD的垂线 ,垂足分别 In the 20th year of 2010, the first question of the first question of the Tianjin Intermediate Test Paper was: The diagonal of the known quadrilateral ABCD intersects with BD at point O. If S△AOB =4, S△COD =9, then the quadrangle The minimum value of the area AB of the ABCD quadrilateral ABCD is A 2 1 B 2 5 C 2 6 D 36 Figure 1 We give the following solution to the analysis and evaluation of the test questions. The solution is shown in Figure 1, over the points A and C for the BD. Vertical line, vertical foot