证明:设AB=AC=2X,则AE=BE=X;AD=AB+BD=2AB=4X.
AC^2=(2X)^2=4X^2; AE*AD=X*(4X)=4X^2.
即:AC^2=AE*AD,AC/AE=AD/AC;
又∠A=∠A,则⊿CAE∽⊿DAC;
故CD/CE=AC/AE=AB/AE=2,即CD=2CE.
证明:设AB=AC=2X,则AE=BE=X;AD=AB+BD=2AB=4X.
AC^2=(2X)^2=4X^2; AE*AD=X*(4X)=4X^2.
即:AC^2=AE*AD,AC/AE=AD/AC;
又∠A=∠A,则⊿CAE∽⊿DAC;
故CD/CE=AC/AE=AB/AE=2,即CD=2CE.