证明:∠ACE=∠B,∠CAE=∠BAC.则⊿CAE∽⊿BAC,AC/AE=AB/AC,AC^2=AE*AB;
∠ADC=∠BAC=90度,∠ACD=∠BCA,则⊿ACD∽⊿BCA,AC/CD=BC/AC,AC^2=CD*CB.
所以,AE*AB=CD*CB.(等量代换)