若
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,则cos2θ=
.
考点分析:
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已知函数f(x)=x
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若a≥0,b≥0,且当
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时,恒有ax+by≤1,则以a,b为坐标的点P(a,b)所形成的平面区域的面积是( )
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D.
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对两条不相交的空间直线a与b,必存在平面α,使得( )
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B.a⊂α,b∥α
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若双曲线
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