1. vector question

ABCD is a straight line

O is a point so that OA = a and OB = b

B is the midpoint of AC
C is the midpoint of AD

Express in terms of a and b the vectors:

(i) AC
(ii) OD

2. Originally Posted by Danielisew
ABCD is a straight line

O is a point so that OA = a and OB = b

B is the midpoint of AC
C is the midpoint of AD

Express in terms of a and b the vectors:

(i) AC
(ii) OD

(i) So $\vec{AC}=2\vec{AB}$ and $\vec{AB}=-\bold{a}+\bold{b}$

(ii) $\vec{OD}=\bold{a}+2 \vec{AC}$

and from these you should be able to complete the answers yourself.

RonL