2  Projection of a vector on a line
Suppose a vector AB
uuur
 makes an angle θ with a given directed line l (say), in the
anticlockwise direction  (Fig 10 20) Then the projection of AB
uuur
 on l is a vector pr
(say) with magnitude | AB | cosθ
uuur
, and the direction of pr  being the same (or opposite)
to that of the line l, depending upon whether cosθ is positive or negative The vector pr
Fig 10