在菱形ABCD中∠AOB=90° AC=2AO BD=2BO BD平分∠ABC∵BD平分∠ABC∴∠ABD=1/2∠ABC=30°∴橡早OA=1/2AB=2cm AC=4cm在Rt△AOB中OB=√梁余雀4方-2方毁羡=2√3∴BD=4√3