如图,在三棱锥P-ABC中,PA⊥平面ABC,AB⊥BC(1)证明:PB⊥BC(2)若PA=AB=BC,秋二面角A-PC-B的大小

如图,在三棱锥P-ABC中,PA⊥平面ABC,AB⊥BC(1)证明:PB⊥BC(2)若PA=AB=BC,秋二面角A-PC-B的大小

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When you feel helpless and ________, just remember you are not ________ in the w

When you feel helpless and ________, just remember you are not ________ in the world because yourfri

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Don’t go out now, it’s raining ________.

Don’t go out now, it’s raining ________.

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—Its ________today.Lets go to the beach. —Sounds great!Dont forget your sunglas

—Its ________today.Lets go to the beach. —Sounds great!Dont forget your sunglasses.

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It is ________ to say“thank you” very often, even to family members.

It is ________ to say“thank you” very often, even to family members.

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