夹角有多大(题目已修改,注意读题) Time Limit: 1000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 10194 Accepted Submission(s): 4072 Problem Descr
为什么两个向量的内积等于模长乘夹角? 已知两个向量 a = [ a 1 , a 2 ] a=[a_1,a_2] a=[a1,a2]和 b = [ b 1 , b 2 ] b=[b_1,b_2] b=[b1,b2],他们的内积为 a b = a 1 b 1 + a 2 b 2 ab=a_1b_1+a_2b_2 ab=a1b1+a2b2,看书上的定义该内积的值是一个