新课程增加了空间向量后,降低了学生空间想象的难度,为解决立体几何的角度和距离问题提供了通用方法,学生可以熟练地用代数方法去计算,去验证.但是在求二面角的大小时,往往需要判断它是锐角还是钝角,学生限于空间想象能力,存在较大困难,文[1]中也给出了一种判定二面角的大小是 After adding the space vector to the new course, the difficulty of the student’s space imagination is reduced, and a general method is provided for solving the problem of the angle and distance of the three-dimensional geometry. The student can skillfully use the algebraic method to calculate and verify. However, in the dilemma, For large hours, it is often necessary to determine whether it is an acute angle or an obtuse angle. Students are limited in their ability to imagine space and there is a great difficulty. In [1], the size of a dihedral angle is also given.