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题目如图1,在五棱锥S-ABCDE中,SA⊥底面ABCDE,SA=AB=AE=2,BC=DE=3,∠BAE=∠BCD=∠CDE=120°.图1()求异面直线CD与SB所成的角(用反三角函数值表示);()证明:BC⊥平面SAB;()用反三角函数值表示二面角B-SC-D的大小(本小问不必写出解答过程).题目中的第()问设计新颖,以填空题的试题
The title is shown in Figure 1. In the pentagonal pyramid S-ABCDE, the SA bottom surface ABCDE, SA = AB = AE = 2, BC = DE = 3, ∠ BAE = ∠ BCD = ∠ CDE = 120 °. Figure 1 () Seeking differences The angle formed by the surface straight line CD and SB (indicated by the inverse trigonometric function value); () Proved by: BC ⊥ plane SAB; () The value of the dihedral angle B-SC-D is represented by the inverse trigonometric function value. Write the answer process.) The first question in the title asks for a novel design to fill in the blank questions.