如图，在正方体ABCD﹣A1B1C1D1中，点M，N分别是面对角线A1B与B1D1的中点，若DA→=a→，DC→=b→，DD1→=c→，则MN→=_刷题宝

题干

如图，在正方体ABCD﹣A₁B₁C₁D₁中，点M，N分别是面对角线A₁B与B₁D₁的中点，若DA→=a→，DC→=b→，DD1→=c→，则MN→=（　　）

A： $\frac{1}{2}$ ( $\vec{c}$ + $\vec{b}$ - $\vec{a}$ )

B： $\frac{1}{2}$ ( $\vec{a}$ + $\vec{b}$ - $\vec{c}$ )

C： $\frac{1}{2}$ ( $\vec{a}$ - $\vec{c}$ )

D： $\frac{1}{2}$ ( $\vec{c}$ - $\vec{a}$ )

上一题下一题 0.0难度选择题更新时间:2016-02-15 06:50:21

答案(点此获取答案解析）

D

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