50, 看这儿

来源: math-fan 于 2018-02-11 13:15:35 [档案] [旧帖] [给我悄悄话] 本文已被阅读：次 (402 bytes)

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回答: 刚刚，又卡住了，你们也看看由 Vaillan 于 2018-02-11 11:46:53

since we know AE and ED, so we easily know the length of AD=BC= sqrt(21^2+72^2)= 75and CF=sqrt(75^2-45^2)=60,

let's draw a line parallel to AD pass point F, it interacts with AD at point G, and interacts with BC at point H,

then found length of FH=36 and BH=AG=27, then we found GH= 14 in triangle of GFD,

AB=FH+GF=36+14=50.

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