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Homework Help: Angle between diagonals of a cube

  1. Jul 7, 2008 #1
    1. The problem statement, all variables and given/known data
    Find the acute angle between two diagonals of a cube.

    2. Relevant equations

    3. The attempt at a solution
    I know that the length of a diagonal of a cube whose side lengths are each one is sqrt(3), so I think it has something to do with that. Other than that, I'm drawing a blank. I could use the unit vectors <1,0,0> and <0,1,0> and find the angle between them, but that's not giving me the right answer.
  2. jcsd
  3. Jul 7, 2008 #2


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    Homework Helper

    Here's something you can try. Locate the cube on a coordinate axis, and determine the coordinates of is corners. Then find the vectors corresponding to the cube diagonals and make use of the definition of the dot product.
  4. Jul 7, 2008 #3


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    Homework Helper

    Draw a cube and sketch in a face diagonal and a space diagonal.
    Then draw two triangles and smile.
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