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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
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