过点A作AE⊥BC于E,过点D作DF⊥BC于F∵AE⊥BC,DF⊥BC,AD∥BC∴矩形AEFD∴EF＝AD∵AB＝CD＝8∴∠BCD＝∠B＝60∴BE＝AB/2＝4,CF＝CD/2＝4,AE＝AB×√3/2＝8×√3/2＝4√3∴CE＝BC-BE＝12-4＝8,EF＝BC-BE-CF＝4∴AD＝4,A...