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题目 正三棱锥相邻两侧面所成的角为α,则α的取值范围是 ( ) .(A) (0°,1 80°) (B) (0°,6 0°)(C) (6 0°,90°) (D) (6 0°,1 80°)分析 正棱锥的底面为正多边形 ,且顶点在底面上的射影为底面正多边形的中心 .图 1如图 1 ,点 O为正△ ABC的中心 ,我们可设想面OAB
The angle formed by the adjacent two sides of the positive triangular pyramid is α, then the range of α is () (A) (0°, 180°) (B) (0°, 60°) (C) ( 6 0°, 90°) (D) (6 0°, 180°) Analyze the base of the positive pyramid as a regular polygon, and the projection of the vertex on the bottom surface is the center of the base polygon. Figure 1 As shown in Figure 1, Point O For the positive △ ABC center, we can imagine the face OAB