求二面角是立体几何中的重点和难点,也是高考中的热点问题.用以往“从形到形”推理方法,即要求学生根据提设条件,找到二面角的平面角,再由线面、线线等关系计算出结果.但对许多学生来说,掌握这种“从形到形”的推理方法比较困难.若利用向量法求二面角操作起来简单易行,学生容易 Seeking dihedral angle is the focus and difficulty in the three-dimensional geometry, but also hot topic in college entrance examination.Using past “from shape to shape” reasoning method, which requires students to find the dihedral plane angle according to the proposed conditions, and then by the line Surface, lines, etc. However, for many students, it is difficult for many students to master this “form-to-shape” reasoning method, and it is easy for students to use the vector method to find the dihedral angle for easy operation