? 發問於 科學及數學數學 · 7 月前

Maths problem, hiw to do.thanks?

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  • 匿名
    7 月前
    最愛解答

    Question:

    In the figure, ACF, BCD and EFG are straight lines. BD//EG, AC = 1, CD = 1.5, CF = 2, FG = 3 and CG = 4. Find the length of AD.

    https://s.yimg.com/tr/i/98813e72e4614b1caa3d583124...

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    Solution:

    In △ACD and △CFG,

    AC/CF = 1/2 = 1.5/3 = CD/FG ...... ( given )

    ∠ACD = ∠CFG ...... ( alt. ∠s, BD//EG )

    ∴ △ACD ≅ △CFG ...... ( ratio of 2 sides, inc. ∠ )

    ∴ AD/CG = 1/2 ...... ( corr sides, ~ △s )

       AD = (4)/2 = 2

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    Remark:

    https://s.yimg.com/tr/i/98813e72e4614b1caa3d583124...

    In the picture, the length of CD seems to be equal to the length of AC, but AD is still parallel to CG.

    Correct ratio

    https://s.yimg.com/tr/i/6a319d67603c4f9896721ce463...

    Attachment image
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