Gaokao Math Practice Question
已知正四棱雉 $S-A B C D$ 的侧棱长与底面边长都相等, $E$ 是 $S B$ 的中 点, 则 $A E$、 $S D$ 所成的角的余弦值为($\qquad$)
- A.$\frac{1}{3}$
- B.$\frac{\sqrt{2}}{3}$
- C.$\frac{\sqrt{3}}{3}$
- D.$\frac{2}{3}$
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