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Math Help - Proof

  1. #1
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    Proof

    Down to my last problem!

    Suppose that point Q is not on line m. Prove that there is only one line through Q that is perpendicular to m.


    ( I know Playfair's postulate is similar, stating there is only one line through point Q that is parallel to m. But wasn't sure how to proceed with proving this one).
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  2. #2
    MHF Contributor

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    Do you know (have proven) there is some line through Q and perpendicular to l? If so, suppose there is a second line. There will be formed a triangle with two right angles. That is impossible.

    If you have no proven there is some line through Q and perpendicular to l then that is your first task.
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