Question

If `vecr=xhati+yhatj+zhatk` ,find `(vecrxxhati).(vecrxxhatj)+xy`

Answer 1

Given

`vecr=xhati+yhatj+zhatk`

`(vecrxxhati).(vecrxxhatj)+xy`

`=[(xhati+yhatj+zhatk)xxhati].[(xhati+yhatj+zhatk)xxhatj]+xy`

`=[(xhatixxhati+yhatjxxhati+zhatkxxhati)].[(xhatixxhatj+yhatjxxhatj+zhatkxxhatj)]+xy`

`=(0hati-yhatk+zhatj).(xhatk+0hatj-zhati)+xy`

`=(0z-xy+0z)+xy`

`=-xy+xy`

`=0`