解：?$(1)△AFC∽△BFA$?
∵?$AD$?是?$△ABC$?的角平分線
∴?$∠BAD=∠CAD$?
∵?$EF$?垂直平分?$AD$?
∴?$AF=DF$?
∴?$∠EAF=∠EDF$?
∴?$∠EAF-∠DAC=∠EDF-∠BAD，$?即?$∠CAF=∠B$?
又?$∠AFC=∠BFA$?
∴?$△AFC∽△BFA$?
?$(2)DF$?是?$FB、$??$FC$?的比例中項(xiàng)
∵?$△AFC∽△BFA$?
∴?$\frac {AF}{FC}=\frac {FB}{AF}$?
∴?$AF^2=FB · FC$?
又?$AF=DF$?
∴?$DF^2=FB · FC$?
∴?$DF$?是?$FB、$??$FC$?的比例中項(xiàng)
