题目内容
如图,⊙O内切于△ABC,切点分别为D、E、F,且DE//BC, 若AB=8cm,AD=5cm,则△ADE的周长是 cm; 


∵⊙O内切于△ABC,切点分别为D、E,F∴AD=AE="5cm,BD=BF=AB-AD=8-5=3" cm,FC="EC" ∵DE//BC ∴AD/BD="AE/EC," ∴EC="3" cm, ∵AD/AB="DE/BC," ∴DE=
cm,△ADE的周长=AD+AE+DE=5+5+
=




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