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How many right triangles can you create with given coordinates?

  1. Mar 13, 2009 #1
    Hello!
    I have one question.
    I have given 5 coordinates:
    0 0
    2 0
    1 1
    1 -1
    3 -1

    The question is how many right angles can I create with these coordinates?
    I know one way out, but it is pretty complicated.
    C52=5!/(2!*3!)=5*4*3!/(2!*3!)=10
    And try every single combination (finding the sides of the triangles, there are 10 of them). Is there any simpler way?

    Thanks in advance.
    Regards.
     
  2. jcsd
  3. Mar 13, 2009 #2
    I'm not sure how you tested to see if the triangles are right, but the fastest way is to find the slope of the lines between each two points. Perpendicular lines have slopes which are negative reciprocals of each other.
     
  4. Mar 13, 2009 #3
    you never made sure that the angles you'll get will be all right angles.
     
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