下列说法中,正确的个数为( ) (1) AB + MB + BC + OM + CO = AB (2)已知向量 a =(6,2)与 b =(-3,k)的夹角是钝角,则k的取值范围是k<0 (3)若向量 e 1 =(2,-3), e 2 =( 1 2 ,- 3 4 ) 能作为平面内所有向量的一组基底 (4)若 a ∥ b ,则 a 在 b 上的投影为 | a | .
【简答题】Industrial engineering (IE) is emerging as one of the classic and novel professions that will be counted for solving complex and systematic problems in the highly technological world of today.