Saturday, January 4, 2025

Geometry Problem 1587: Uncover the Elegance of Triangle BGH's Area in Trapezoid ABCD.

Challenging Geometry Puzzle: Problem 1587. Share your solution by posting it in the comment box provided.
Audience: Mathematics Education - K-12 Schools, Honors Geometry, and College Level.

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Illustration of Geometry Problem 1586

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2 comments:

  1. https://photos.app.goo.gl/swEXmgUgZ8QwJejB8


    Define point K per sketch
    S(ABCD)= 36 => h= 8 ( see sketch)
    And GB/GF=2/3
    Apply Ceva theorem with point H in triangle ABF
    AE/EF x GF/GB x KB/KA=1
    Replace values of AE/EF and GF/GB in above we get KA=KB

    Apply Van aubel’s theorem for point H in triangle ABF
    BH/HE= KB/KA + GB/GF
    We get BH/BE= ⅝
    S(BEF)= ½. 6.8= 24
    S(BGH)/S(BEF)= (BH. BG)/(BE.BF)= ⅝ x ⅖= ¼
    So S(BGH)= 6

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  2. triangle BCG ~ triangle FDG
    BC:FD=2:3 → put S(BCG)=4k , S(FDG)=9k
    FD:DA=3:7→S(ADG)=21k
    FG:GB=3:2→S(GBA)=20k
    ∴S(ABCD)=S(BCG)+S(ADG)+S(GBA)=4k+21k+20k=45k
    45k=36
    k=4/5
    S(GBA)=16
    menelauss theorem (AH/HG)*(2/5)*(6/4)=1
    ∴AH:HG=5:3

    S(BGH)=(HG/AG)*S(ABG)=(3/8)*16=6

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