题目
题型：不详难度：来源：
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答案
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因为|
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∴
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即
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故答案为：-
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核心考点
试题【设a、b为两非零向量，且满足|a|=3|b|=|a+2b|，则两向量a、b的夹角的余弦值为______．】；主要考察你对平面向量模和夹角的坐标表示等知识点的理解。[详细]
举一反三
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题型：
|=0}是单元素集合．
（1）求
与
的夹角
（2）若关于t的不等式|
-t
|＜|
-m
|的解集为空集，求实数m的值．
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（1）求
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（2）若关于t的不等式|
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A．[
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