题目如图,⊙O⊙O⊙O是四边形ABCDABCDABCD的内切圆,切点为EEE,FFF,GGG,HHH,已知AD/ /BCAD/\!/BCAD//BC,AB=CDAB=CDAB=CD,DO=6cmDO=6cmDO=6cm,CO=8cmCO=8cmCO=8cm,求四边形ABCDABCDABCD的周长.知识点:切线长定理章节:图形的性质 / 圆