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在一次射击训练中,某一小组10名成员的成绩如表: 环数 7环以下 7环 8环 9...
在一次射击训练中,某一小组10名成员的成绩如表:
已知该小组的平均成绩为8.3环,则xy的值为( )
A.0
B.4
C.5
D.6
考点分析:
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,
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|=1,|
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|=2,
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的夹角大小是( )
A.60°
B.90°
C.120°
D.150°
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已知
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,则tan2α=( )
A.
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C.
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D.
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若直线ax+y+1=0与直线2x+y+2=0平行,则实数a的值为( )
A.2
B.-2
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D.
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设集合A={0,1,2},B={1,2,3},则 A∩B=( )
A.{0,1,2,3}
B.{0,3}
C.{1,2}
D.∅
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△ABC的面积是30,内角A,B,C所对边长分别为a,b,c,cosA=
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;
(Ⅱ)若c-b=1,求a的值.
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