A:前提错误,结论正确
B:前提正确,结论错误
C:前提错误,结论错误
D:前提正确,结论正确
"What happened?" he asked me in .
如图,在▱ABCD中,点E是AD的中点,延长BC到点F,使CF:BC=1:2,连接DF,EC.若AB=5,AD=8,sinB=45,则DF的长等于( )