众多教辅书上有这样一道题 :已知ＰＯ⊥平面α ,0为垂足 ,Ａ、Ｂ是α内与 0不共线的两点 ,判断∠ＡＯＢ与∠ＡＰＢ的大小 .所给答是∠ＡＯＢ ∠ＡＰＢ ,这个答案是错误的 .解答本题有相当大的难度 ,命成选择题或填空题都不太合适 .现对本题讨论如下 :由∠ＯＡＢ与∠ＯＢＡ中至 Many supplementary books have such a question: Known PO ⊥ plane α, 0 for the foot, A, B is two points in the α and 0 are not collinear, determine the size of ∠AOB and ∠APB. The answer is ∠AOB ∠APB, this answer is wrong. There are considerable difficulties in answering this question, and it is not appropriate to make a multiple-choice or fill-in question. Now this topic is discussed as follows: From ∠ OAB and ∠OBA