二面角既是立体几何教学的重点,又是难 点,同时也是历年高考命题的热点.下面介绍 二面角求解的向量策略: 1.半平面垂棱向 夹角法 如图1,若CE⊥AB 于E,DF⊥AB于F,则二 面角C-AB-D的大小 等于向量EC与FD的夹角arccosEC·FD/|EC|·|FD| The dihedral angle is not only the focal point but also the difficult point of the three-dimensional geometry teaching. It is also the hot spot of the college entrance examination proposition in the past years. The following describes the vector strategy for solving the dihedral angle: 1. The half-plane vertical rake angle method is shown in Figure 1, if CE⊥AB At E, DF ⊥ AB at F, the dihedral angle C-AB-D is equal to the angle between the vector EC and FD arccosEC·FD/|EC|·|FD|