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 20
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 MATHEMATICS
444
is called the projection vector, and its magnitude | pr | is simply called as the projection
of the vector AB
uuur
 on the directed line l