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Math Help - geometry prove

  1. #1
    Newbie parmis's Avatar
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    geometry prove

    prove it thx!
    Attached Thumbnails Attached Thumbnails geometry prove-gggg.jpg  
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  2. #2
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    Re: geometry prove

    If it said AE/AF = CD/BD, then both cross-products would equal the area of the parallelogram.
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  3. #3
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    Re: geometry prove

    Emakarov is right this ratio is not valid : it is valid only if ABCD is a rombus.
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  4. #4
    Newbie parmis's Avatar
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    Re: geometry prove

    Quote Originally Posted by MINOANMAN View Post
    Emakarov is right this ratio is not valid : it is valid only if ABCD is a rombus.
    ABCD is a rhombus. how should i prove this ratio?
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  5. #5
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    Re: geometry prove

    As I said in post #2, AE * BD = AF * CD = area of the rhombus.
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  6. #6
    Newbie parmis's Avatar
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    Re: geometry prove

    geometry prove-gggg.jpg
    answer these too. thx
    in 1, question is: What fraction of the ABCD rhombus's area is the MNP Triangle's area?
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  7. #7
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    Re: geometry prove

    Hint: area of △MNP = area of △MPB because MP is the median. And area of △MNB = 1/2 area of MBCN.
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  8. #8
    Newbie parmis's Avatar
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    Re: geometry prove

    Quote Originally Posted by emakarov View Post
    Hint: area of △MNP = area of △MPB because MP is the median. And area of △MNB = 1/2 area of MBCN.
    I undrestand area of △MNP= area of △MPB but why area of △MNB = 1/2 area of MBCN?
    why area of △BNC = 1/2 area of MBCN?
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  9. #9
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    Re: geometry prove

    Quote Originally Posted by parmis View Post
    why area of △MNB = 1/2 area of MBCN?
    Because MBCN is a parallelogram and BN is a diagonal, which divides the parallelogram into two equal triangles.
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  10. #10
    Newbie parmis's Avatar
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    Re: geometry prove

    Thank you very much.
    someone prove rhombus's area formula that i wrote up in picture in 6#.
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  11. #11
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    Re: geometry prove

    Generally, you should start a new thread for each new question. People are far less likely to read through several posts to discover that there is an unanswered question in the end.
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