∵∠BAC=90°，AB=AC，∴∠B=∠ACB=45°，∵BD=BA，∴∠BAD=∠BDA= 1 2 （180°-45°）=67.5°，∵CE=CA，∴∠E=∠CAE= 1 2 ×45°=22.5°，∴∠DAE=∠BAD-∠E，=67.5°-22.5°，=45°．
