题目如图,ABABAB,BCBCBC,CDCDCD分别与圆相切于点EEE,FFF,GGG,AB=BC =CDAB=BC\:=CDAB=BC=CD,连接ACACAC与BDBDBD,相交于点PPP,连接PF.PF.PF.求证:PF⊥BC.PF\bot BC.PF⊥BC.知识点:切线长定理章节:图形的性质 / 圆