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