平面向量基本定理如果e_1、e_2是同一平面内不共线的两个向量,那么对于这个平面内的任一个向量a,有且只有一对实数λ_1、λ_2,使a=λ_1e_1+λ_2e_2.不共线的向量e_1、e_2叫做表示这一平面内的所有向量的一组基底.那么,在具体操作中,怎样用e_1、e_2表示a呢?也就是如何确定λ_1、λ_2的值呢?有以下三种基本方法.一、三角形法则或平行四边形法则 If e_1 and e_2 are two non-collinear vectors in the same plane, then for any vector a in this plane, there is only one pair of real numbers λ_1 and λ_2, so that a = λ_1e_1 + λ_2e_2. The vectors e_1, e_2 of the line are called a set of bases that represent all the vectors in this plane. So how to use e_1 and e_2 to represent a in a concrete operation? That is, how to determine the values ​​of λ_1 and λ_2? There are three The basic method. A triangular law or parallelogram law