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一、提出问题有这样一道立体几何选择题：∠Ａ的顶点在平面Ｍ外，∠Ａ的两边与平面Ｍ相交于Ｂ、Ｃ两点，∠Ａ所在平面与平面Ｍ斜交，则∠Ａ与∠Ａ在平面Ｍ上的射影角∠Ａ１的大小关系是（）．Ａ．∠Ａ＞∠Ａ１Ｂ．∠Ａ＜∠Ａ１Ｃ．∠Ａ≤∠Ａ１Ｄ．∠ＡＡ１本题正确答案...
1. Asking questions There is a three-dimensional geometric multiple-choice title: When the vertex of ∠A is in plane M, both sides of ∠A intersect with plane M at two points B and C. The plane where ∠A intersects with plane M is skewed. The magnitude of the projection angle ∠A1 of ∠A on the plane M is (). A. ∠ A> ∠ A1B. ∠A<∠A1C. ∠A≤∠A1D. ∠AA1 correct answer for this question...