我们把既有大小又有方向的量叫做向量,这就是向量的本质,它揭示了向量具有“数”和“形”的双重身份.从代数角度看,由于借助数量积公式可将向量问题实数化,所以向量问题可利用数的性质加以处理.从几何角度看,由于向量的模、向量加减法的平行四边形法则和三角形法则、向量的平行与垂直等都有明显的几何意义,所以向量问题可利用数形结合思想加以处理.那么,在具体解题时,如何巧妙利用向量的双重身份呢?请看 We call both the size and the direction of the vector, which is the essence of the vector, which reveals that the vector has the dual identities of “number” and “shape.” From an algebraic perspective, Since vector problems are realizable, the vector problem can be dealt with by the nature of the number.From the geometric point of view, due to the vector modulo, vector addition and subtraction method of parallelogram and triangle law, vector parallel and vertical have obvious geometry Therefore, the problem of vector can be dealt with by the combination of number and form. So, how to skillfully use the dual identity of vector when solving the problem?