What is the projection of $<4,9,1 >$ onto $<-1,7,2 >$ ?

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Answer 1 · 2016-04-07T14:38:00

$61/sqrt54$

$vec A={4,9,1}$ and $vec B={-1,7,2}$

Projection of $vec A$ on $vec B$ is the dot product of $vec A$ and unit vector $vec B$ .

Hence;
$vec A * hat B$
$=vec A * (vec B)/(|vec B|)$
$={4,9,1}.({-1,7,2})/(sqrt(1^2+7^2+2^2))$
$=(4*(-1)+9*7+1*2)/sqrt54$
$=61/sqrt54$

What is the projection of <4,9,1 ><4,9,1 > onto <-1,7,2 ><-1,7,2 >?