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在△ABC中,已知sin2A=sin2B+sinBsinC+sin2C,则A等于...
在△ABC中,已知sin2A=sin2B+sinBsinC+sin2C,则A等于( )
A.30°
B.60°
C.120°
D.150°
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的图象,只需将函数y=sin2x的图象( )
A.向左平移
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B.向右平移
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C.向左平移
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D.向右平移
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在△ABC中,由已知条件解三角形,其中有两解的是( )
A.b=20,A=45°,C=80°
B.a=30,c=28,B=60°
C.a=14,b=16,A=45°
D.a=12,c=15,A=120°
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已知{a
n}是等差数列,a
10=10,其前10项和S
10=70,则其公差d=( )
A.
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D.
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已知
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、
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均为单位向量,它们的夹角为60°,那么|
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|=( )
A.
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B.
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C.
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D.4
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