解:∵AB=14 ∴ ∴AD = 5cm BD = 9cm 又CD⊥AB ∴CB2 = BD2 +CD2 = 92 + 122 = 225 ∴CB = 15cm AC2 = AD2 + CD2 = 52+ 122 = 169 ∴AC = 13cm ∴△ABC的周长为42cm 又 DE//BC ∴△ADE∽△ABC ∴△ADE的周长为15cm
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