设a,b是两个单位向量,命题p:“(2a+b)⊥b”是命题a:“a•b”的夹角等 发布时间:2017-04-15 08:42 │ 来源:www.tikuol.com 题型:选择题 问题: 设a,b是两个单位向量,命题p:“(2a+b)⊥b”是命题a:“a•b”的夹角等于2π3成立的( )A.充分不必要条件B.必要不充分条件C.充要条件D.既不充分也不必要条件
题型:选择题 — Is Alice still performing? — I’m afraid not. She is said the stage already as she has gone abroad for further study.A.to leaveB.to have leftC.to be leftD.to have been left 查看答案
题型:选择题 某有机物X加氢反应后的还原产物是CH3CH(CH3)CH2OH,关于X的下列说法正确的是( )A.X可能是乙醛的同系物B.X可能是正丁醇的同分异构体C.X可能是乙烯的同分异构体D.X分子中可能有碳碳双键 查看答案