Question

在矩形abcd中 ab=3,ad=2,向量dc=3向量de,则向量ab乘向量ae等于

Answer 1

明显地 AB丄AD,所以向量 AB*AD = 0 ,
所以 AB*AE=AB*(AD+DE)
=AB*AD+AB*DE
=0+AB*DE
=AB*DE
=AB*1/3*DC
=AB*1/3*AB)
= 1/3*AB^2
= 1/3*3^2
= 3 .