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张景中先生说,内积的另一种用法,是用某个向量a点乘一个向量等式的两端,把和a垂直的向量消去,达到简化等式的目的.不少有几何图形背景的求数量积问题,背景中的垂直关系是解题的关键.这类试题可能正是体现了这种简化思想,下面举几例,揭示这类问题的解法规律,与读者分享.例1(2012年北京高考题)已知正方形ABCD的边长为1,点E是AB边上的动点,则
Mr. Zhang Jingzhong said another use of the inner product is to multiply both ends of a vector equation by a vector a and eliminate the vector perpendicular to a to simplify the equation. Many geometric background The question of the number of products, the background of the vertical relationship is the key to solving problems .This type of questions may be the embodiment of this simplified thinking, the following to name a few examples to reveal the law of solution to such problems, and readers to share. Example 1 (2012 Year Beijing college entrance examination) Known square ABCD side length of 1, point E is the moving point AB edge, then