(1)RT△ABC中,∠C=90,∠B=30.所以∠CAB=60
AD平分∠CAB,所以∠BAD=∠CAB/2=30
∠BAD=∠B,所以AD=DB
(2)△ABC和△AEF中
∠A=∠A,∠AFE=∠C=90
所以△ABC∽△AEF,AE:AB=AF:AC
RT△ABC中,∠B=30,所以AB=2AC=12
AE=AC-CE=6-X,AF=AB-BF=12-Y
(6-X):12=(12-Y):6
6-X=2(12-Y)
6-X=24-2Y
2Y=18+X
Y=(18+X)/2=X/2+9
(3)RT△ACD中,∠CAD=∠CAB/2=30
所以AC:CD=√3,CD=2√3
由(2)中三角形相似得:∠AEF=∠B=30
RT△AEF中,AE=2AF
∠DEF=90,所以∠DEC=180-90-30=60
RT△CDE中,CD=√3CE,所以CE=2
AE=AC-CE=4
AF=AE/2=2
BF=AB-AF=10