向量在立体几何空间元素位置关系的证明和空间元素量、空间元素量的关系的求解中有着广泛的应用,应用向量解立体几何题的一般方法有基底向量法和坐标向量法,应用基底向量法时必须选择适当的基底,应用坐标向量法时必须选择适当的坐标系.例1 如图1,已知正四棱柱 ABCD-A_1B_1C_1D_1的 The vector has a wide range of applications in the proof of the position relationship of elements in the three-dimensional geometric space and the solution of the relationship between the amount of space elements and the amount of space elements. The general methods of solving the three-dimensional geometric problems with vector solutions are the base vector method and the coordinate vector method, and the application of the base vector method. The appropriate base must be selected, and the appropriate coordinate system must be selected when applying the coordinate vector method. Example 1 As shown in Figure 1, the known positive square prism ABCD-A_1B_1C_1D_1