∠DAB=135°
连接AC,设DA=a
所以AB=2a =BC,CD = 3a
AB=BC,∠ABC=90°========> AC = 2√2 a,∠BAC =45°
所以AD"+AC" = CD"
所以∠DAC=90°
所以∠DAB=∠DAC+∠BAC=135°
∠DAB=135°
连接AC,设DA=a
所以AB=2a =BC,CD = 3a
AB=BC,∠ABC=90°========> AC = 2√2 a,∠BAC =45°
所以AD"+AC" = CD"
所以∠DAC=90°
所以∠DAB=∠DAC+∠BAC=135°