上游究通大粤 SHANGHAI JLAO TONG UNTVERSITY Vector dot product: A·B=4B cos0 ii=j.j=k.k=1 ij=j.k=k.i=0Vector dot product: A Bi = ABcosθ i.i = j.j = k.k =1 i.j = j.k = k.i = 0