由于向量融形、数于一体,具有几何形式与代数形式的“双重身份”.向量的数量积是两个向量间的一种乘法运算,数量积隐含着一种不等量的关系,即(|a||b|)~2≥(a·b)~2.这使得向量与不等式问题有着“天然”的联系.而这种不等量的关系可用证明不等式,解决此类问题的基本方法是构造法,因此解题的关键是从所证不等式的结构和特点出发,巧妙构造向量. Because of the vector fusion, the number in one, with geometric form and algebraic form “double identity ” The vector product of the number of products is a multiplication between the two vectors, the number of products implies an unequal amount of relationship , That is, (| a || b |) ~ 2≥ (a · b) ~ 2, which makes the relation between vector and inequality question “natural ”, and this inequality relation can be solved by proving inequality The basic method of the class problem is the construction method, so the key to solve the problem is to formulate the vector wisely from the structure and characteristics of the inequality.