As soon as books ________, the volunteers posted them to the students in Hope Pr

As soon as books ________, the volunteers posted them to the students in Hope Primary School.

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如图, AB 是圆 O 的直径, PA⊥圆 O 所在的平面, C 为圆周上一点, D 为线段PC 的中点. ∠CBA=30° , AB=2PA.(1) 证明:

如图, AB 是圆 O 的直径, PA⊥圆 O 所在的平面, C 为圆周上一点, D 为线段PC 的中点. ∠CBA=30° , AB=2PA.(1) 证明: 平面 ABD⊥平面 PBC.(2) 若

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某几何体的三视图如图所示, 则该几何体的体积是()

某几何体的三视图如图所示, 则该几何体的体积是()

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—Will you please show me how to operate the new machine?—Sure. It’s a piece of c

—Will you please show me how to operate the new machine?—Sure. It’s a piece of cake. Now let me tell

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如图,△ABC中,AB=AC,∠B=72°,∠ACB的平分线CD交AB于点D,则点D是线段AB的黄金分割点.若AC=2,则BD=______.

如图,△ABC中,AB=AC,∠B=72°,∠ACB的平分线CD交AB于点D,则点D是线段AB的黄金分割点.若AC=2,则BD=______.

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