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Math Help - The Dot Product - State the angle between the 2 vectors

  1. #1
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    Talking The Dot Product - State the angle between the 2 vectors

    Staet the angle between the two vectors:

    I got

    a) 70

    b) 130

    but not sure.
    Please help, appreciate all pointers!
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by advancedfunctions2010 View Post
    Staet the angle between the two vectors:

    I got

    a) 70

    b) 130

    but not sure.
    Please help, appreciate all pointers!
    You do realise that for a line incidend on another line the two angles on the same side of the second line sum to 180 degrees?

    CB
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  3. #3
    MHF Contributor

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    If you mean that a is a vector making an angle of 100 degrees with the x-axis, up and to the right, and that b is an angle making an angle of 30 degrees with the x-axis, down and to the left, then you simply add those two angles. But I don't understand why you are giving two answers. Those two vectors have one angle between them.
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by HallsofIvy View Post
    If you mean that a is a vector making an angle of 100 degrees with the x-axis, up and to the right, and that b is an angle making an angle of 30 degrees with the x-axis, down and to the left, then you simply add those two angles. But I don't understand why you are giving two answers. Those two vectors have one angle between them.
    There are two questions, question a) and question b) as far as I can see, and both the proposed answers are wrong (for the reasons I hinted at).

    CB
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