Question

若非零向量a，b满足|a|＝|a＋b|＝1，a与b夹角为120°，则 | b | =        ．

Answer 1

1

因为非零向量a，b满足|a|＝|a＋b|＝1，a与b夹角为120°则| b |²=b²，
|a＋b|²＝1= b²+ a²+2ab,可知| b |=1