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Diagonal of rectangle

  1. Apr 1, 2005 #1
    I have problem on this one:

    Using vectors,show that if a diagonals of rectangle are orthogonal then the rectangle must be square.
  2. jcsd
  3. Apr 1, 2005 #2


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    Set up a coordinate system so that one corner of the rectangle is at the origin, the two sides are along the positive x and y axes. Then the corners of the rectangle are at (0,0), (w,0), (0,h), (w,h).

    One of the diagonals, from (0,0) to (w,h) is given by the vector wi+ hj.
    The other, from (w,0) to (0,h) is given by the vector -wi+ hj

    If the two diagonals are orthogonal then their dot product must be 0.

    What IS the dot product of wi+ hj and -wi+ hj?

    What does that tell you about w and h?
  4. Apr 1, 2005 #3
    super,thanx professor
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