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Math Help - Angle between a vector and the y-axis

  1. #1
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    Angle between a vector and the y-axis

    Determine the angle that the vector a = (12, -3, 4) makes with the y-axis.

    Would I still use the dot product? I'm confused on how I would go about do it as I'm not too familiar with three dimensional vectors. All help appreciated!
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  2. #2
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    Quote Originally Posted by IanCarney View Post
    Determine the angle that the vector a = (12, -3, 4) makes with the y-axis.
    \mathbf{j}=<0,1,0>.
    Find \arccos \left( {\frac{{a \cdot j}}{{\left\| a \right\|}}} \right)
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  3. #3
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    Quote Originally Posted by Plato View Post
    \mathbf{j}=<0,1,0>.
    Find \arccos \left( {\frac{{a \cdot j}}{{\left\| a \right\|}}} \right)
    Okay I think I got it. I was doing something wrong before so I got a different answer than the book. Thanks again for all your help!
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