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Math Help - vectors

  1. #1
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    vectors

    determine a vector in the yz plane that is equally inclined to both the y and z axes and has the same length as p= 5i-7j+6k
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by valvan View Post
    determine a vector in the yz plane that is equally inclined to both the y and z axes and has the same length as p= 5i-7j+6k
    trick question? take \| \vec p \| \left< 0, \frac 1{\sqrt 2}, \frac 1{\sqrt 2} \right> (this is the length of the vector p times the unit vector in the yz-plane that is at an angle of 45 degrees to each of the positive y and z axes)
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  3. #3
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    thanks

    awesome thanks, yup its a trick question, this is for my engineering class, our teachers gives us the similar problems all worded differently.
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  4. #4
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    I don't see how that is in any sense a "trick" question, unless you mean by that a question so simple you think there must be some hidden trick.

    One "vector in the yz plane that is equally inclined to both the y and z axes" is, of course, <0, 1, 1>. That has length \sqrt{0^2+ 1^2+ 1^2}= \sqrt{2} so a unit vector in that direction is \left<0, \frac{1}{\sqrt{2}}, \frac{1}{\sqrt{2}}\right>, the vector Jhevon uses. Multiply that vector by the length of 5i- 7j+ 6k which is \sqrt{5^2+ 7^2+ 6^2}= \sqrt{110}.

    Of course, that vector multiplied by -1 gives a second, equally correct, answer.
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