证明:过点C作CE‖AD交BA的延长线于点E,
∵CE‖AD, ∴∠BAD=∠E, ∠DAC=∠ACE,
∵AD为角平分线,∴∠BAD=∠DAC, ∴∠E=∠ACE, ∴AE=AC,
∵CE‖AD, ∴BA/AE=BD/DC, ∴AB/AC=BD/DC
证明:过点C作CE‖AD交BA的延长线于点E,
∵CE‖AD, ∴∠BAD=∠E, ∠DAC=∠ACE,
∵AD为角平分线,∴∠BAD=∠DAC, ∴∠E=∠ACE, ∴AE=AC,
∵CE‖AD, ∴BA/AE=BD/DC, ∴AB/AC=BD/DC