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How do you find the projection of u=<4,8> onto v=<-1,2>?

1 Answer

Vinícius Ferraz

May 28, 2017

#(-12/5, 24/5)#

Explanation:

#u * v = ||u|| * ||v|| * cos theta#

But you want #||u|| * cos theta * hat v = frac{u * v}{||v||} * frac{v}{||v||} = frac{u*v}{v*v}*v#

#= frac{4(-1) + 8*2}{(-1)^2 + 2^2} * (-1, 2)#

#= frac{12}{5} * (-1, 2)#

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