题库 高中数学
题干
已知正方形ABCD的边长为1, 
="a," 
="b," 
=c,则|a+b+c|等于 .
="a," ="b," =c,则|a+b+c|等于 .答案(点此获取答案解析）
="a," ="b," =c,则|a+b+c|等于 .
是夹角为
的单位向量，若
，则
.
|
＋
|＝|
|，则
＝______.
，|
+
|=|
|，则
= ．
是等边三角形，且
,那么四边形ABCD的面积为( )
－
＋
＝
＋
＋
－
＝