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Math Help - Find a vector v with a given magnitude in the direction

  1. #1
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    Find a vector v with a given magnitude in the direction

    Find the vector v with magnitude 2.7 in the direction of w = < 1, -2, -1 >

    This is what i have so far and i will point out where i am stuck.


    || w ||  = \sqrt {1^2 + (-2)^2 + (-1)^2 } = \sqrt 6

     v = 2.7 \frac{w} {|| w ||}

    so, filling in for w we have

      2.7 ( \frac{1} {\sqrt 6}  ,  \frac{-2} {\sqrt 6}  ,  \frac{-1} {\sqrt 6})

    Now, from here do i just multiply the 2.7 to the numerator?

    A Similar problem in my book, the solution manual does something weird and i cant figure it out like

    5 \frac{u} {|| u ||} =  5 < \frac {-1}{\sqrt 5} , \frac{2}{\sqrt5} >

    Then, they go to this final step and i dont see how they are doing that?

    < - \sqrt 5 , 2 \sqrt 5 >
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  2. #2
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    Re: Find a vector v with a given magnitude in the direction

    Quote Originally Posted by icelated View Post
    Now, from here do i just multiply the 2.7 to the numerator?
    Yes.

    Quote Originally Posted by icelated View Post
    A Similar problem in my book, the solution manual does something weird and i cant figure it out like

    5 \frac{u} {|| u ||} =  5 < \frac {-1}{\sqrt 5} , \frac{2}{\sqrt5} >

    Then, they go to this final step and i dont see how they are doing that?

    < - \sqrt 5 , 2 \sqrt 5 >
    Recall that 5/\sqrt{5}=\sqrt{5}.
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  3. #3
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    Re: Find a vector v with a given magnitude in the direction

    thank you
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  4. #4
    Grand Panjandrum
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    Re: Find a vector v with a given magnitude in the direction

    Quote Originally Posted by icelated View Post
    thank you
    Use the thanks button, don't just make a post saying thanks

    CB
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