设向量a.b.c,满足|a|=|b|=1,a*b=-1/2,〈a-c,b-c〉﹦60°,则|c|的中最大值是
问题描述:
设向量a.b.c,满足|a|=|b|=1,a*b=-1/2,〈a-c,b-c〉﹦60°,则|c|的中最大值是
答
⇀ ⇀ ⇀ ⇀∵ |a|=|b|=1,a•b=-12→ →∴ a,b的夹角为120°,→ → → → → → → →→ → → →设 OA=a,OB=b,OC=c则 CA=a-c; CB= b-c则∠AOB=120°;∠ACO=60°∴∠AOB+∠ACO=180°∴A,...