已经非零向量a与b夹角为120度,a·a= - a·b,则|a|/|b|=?
人气：208 ℃ 时间：2020-02-06 04:23:02
解答
0.5
a·a= - a·b
|a|*|a|=-|a|*|b|*cos120度=0.5*|a|*|b|
|a|/|b|=0.5
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