異面直線
a,
b滿足aÌa,bÌb,a∩b=
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,則
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與
a,
b的位置關(guān)系一定是( )
A. 與a,b都相交 | B. 至少與a,b中的一條相交 |
C. 至多與a,b中的一條相交 | D. 至少與a,b中的一條平行 |
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
(本題滿分12分)如圖,在正方體
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中,
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是
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的中點(diǎn).
(1)求證:
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平面
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;(2)求證:平面
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平面
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.
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科目:高中數(shù)學(xué)
來源:不詳
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在四面體
ABCD中,
CB=
CD,
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,且
E,
F分別是
AB,
BD的中點(diǎn),
求證:(I)直線
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;
(II)
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。
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科目:高中數(shù)學(xué)
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如圖,在四棱錐
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中,
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是平行四邊形,

,

分別是
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,
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的中點(diǎn).
求證:

平面

.
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如圖,空間四邊形SABC中,SO⊥平面ABC,O為△ABC的垂心。求證:平面SOC ⊥平面SA
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B。
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科目:高中數(shù)學(xué)
來源:不詳
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科目:高中數(shù)學(xué)
來源:不詳
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設(shè)
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為不重合的兩條直線,

為不重合的兩個平面,給出下列命題:
(1)若
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∥
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且

∥

,則
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∥
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; (2)若
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且
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,則
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∥
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;
(3)若
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∥
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且

∥
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,則
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∥
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; (4)若
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且
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,則
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∥

.
上面命題中,所有真命題的序號是
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科目:高中數(shù)學(xué)
來源:不詳
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a、
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
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科目:高中數(shù)學(xué)
來源:不詳
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