解已知二边和其中一边的对角的三角形,是解三角形教学中的一个难点,产生困难的原因主要是学生只习惯于机械地套用正弦定理.而不理解此类问题有一解、二解和无解三种情况. Solving triangles known to be diagonally opposite sides and sides is a difficult point in solving triangle teaching. The main reason for difficulties is that students are only accustomed to applying the sine theorem mechanically. They do not understand that there is a solution and a second solution to this problem. There are three cases without solution.