若角α的终边经过点P(-1,2)则sinα的值为 .
考点分析:
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平面向量也叫二维向量,二维向量的坐标表示及其运算可以推广到n(n≥3)维向量,n维向量可用(x
1,x
2,x
3,x
4,…,x
n)表示.设
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=(a
1,a
2,a
3,a
4,…,a
n),
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=(b
1,b
2,b
3,b
4,…,b
n),规定向量
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与
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夹角θ的余弦为cosθ=
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.已知n维向量
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,
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,当
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=(1,1,1,1,…,1),
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=(-1,-1,1,1,1,…,1)时,cosθ等于( )
A.
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B.
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C.
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D.
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某化工厂生产一种溶液,按市场要求,杂质含量不能超过0.1%,若最初生产出的溶液含杂质2%,需要进行过滤,且每过滤一次可使杂质含量减少
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,则要使产品达到市场要求至少应过滤( )
A.3次
B.4次
C.5次
D.6次
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设函数f(x)=sin(2x+
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),则下列结论正确的是( )
A.f(x)的图象关于直线x=
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对称
B.f(x)的图象关于点(
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,0)对称
C.把f(x)的图象向左平移
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个单位,得到一个偶函数的图象
D.f(x)的最小正周期为π,且在[0,
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]上为增函数
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已知双曲线
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的一个焦点与抛物线x
2=4y的焦点重合,且双曲线的实轴长是虚轴长的一半,则该双曲线的方程为( )
A.
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B.
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C.
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D.
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下列结论错误的是( )
A.命题“若p,则q”与命题“若¬q,则¬p”互为逆否命题
B.命题p:∀x∈[0,1],e
x≥1,命题q:∃x∈R,x
2+x+1<0,则p∨q为真
C.“若am
2<bm
2,则a<b”的逆命题为真命题
D.若p∨q为假命题,则p、q均为假命题
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