vector{B_(1)D_(1)}=vector{B_(1)A_(1)}+vector{A_(1)D_(1)}
На плоскости A_(1)B_(1)BA:
vector{A_(1)B}=vector{A_(1)A}+vector{A_(1)B_(1)} ⇒ vector{A_(1)B_(1)}=vector{A_(1)B}-vector{A_(1)A}
vector{B_(1)A_(1)}=- vector{A_(1)B_(1)} ⇒
vector{B_(1)A_(1)}=-vector{A_(1)B}+vector{A_(1)A}
vector{B_(1)D_(1)}=-vector{A_(1)B}+vector{A_(1)A}+vector{A_(1)D_(1)}