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Homework Help: Cross product and the angles of a prallelogram

  1. Nov 6, 2009 #1
    Cross product and the angles of a prallelogram's diameters

    1. The problem statement, all variables and given/known data

    With the help of cross product prove: if the angle between the diameters of a parallelogram is 90 degrees, then the parallelogram is a rectangular.

    2. Relevant equations

    A[tex]\times[/tex]B=(surface of the parallelogram)

    3. The attempt at a solution
    Last edited: Nov 6, 2009
  2. jcsd
  3. Nov 6, 2009 #2
    What is [tex] |\mathbf{A} \times \mathbf{B}| [/tex]? How does it depend on the angle between the two vectors?
  4. Nov 6, 2009 #3
    A and B are not the diameters, they are the sides. As I mensioned [tex] |\mathbf{A} \times \mathbf{B}| [/tex]= (the surface of the parallelogram)
  5. Nov 6, 2009 #4


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    Homework Helper

    what are the diameters? the diagonals? if so you should be able to write them as a vector sum of the sides...
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