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Math Help - Show Euclid's Fifth implies Playfair's Postulate

  1. #1
    mdk
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    Show Euclid's Fifth implies Playfair's Postulate

    Can someone help with this? I'm not sure how to show m(angle)DAB + m(angle)ABC is less then 180 degrees. Then to apply Euclid Fifth so t intersects m. Then show t can't intersect m on the "wrong side". Thus t doesn't parallel m and Playfair's postulate holds. See figure.

    Any help would be greatly appreciated...
    Attached Thumbnails Attached Thumbnails Show Euclid's Fifth implies Playfair's Postulate-euclid-vs.-playfair.jpg  
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  2. #2
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    Quote Originally Posted by mdk View Post
    Can someone help with this? I'm not sure how to show m(angle)DAB + m(angle)ABC is less then 180 degrees. Then to apply Euclid Fifth so t intersects m. Then show t can't intersect m on the "wrong side". Thus t doesn't parallel m and Playfair's postulate holds. See figure.

    Any help would be greatly appreciated...
    I'm not clear why you say 'Then show t can't intersect m on the "wrong side" ' Once you have shown that "t intersects m" you are done.
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  3. #3
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    Do you mean you want to prove Post. 5?
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