作AE⊥BC于点E.作AF⊥CD,交CD的延长线于点F
则∠EAF=90°
∵∠BAD=90°
∴∠DAF=∠BAE
∵AB=AD,∠AEB=∠F=90°
∴△ABE≌△ADF
∴AE=AF,S△ABE=S△ADF
∴四边形AECF是正方形,S四边形ABCD=S正方形AECF=24
∴AE=2√6
∴AC=√2AE=4√3cm
作AE⊥BC于点E.作AF⊥CD,交CD的延长线于点F
则∠EAF=90°
∵∠BAD=90°
∴∠DAF=∠BAE
∵AB=AD,∠AEB=∠F=90°
∴△ABE≌△ADF
∴AE=AF,S△ABE=S△ADF
∴四边形AECF是正方形,S四边形ABCD=S正方形AECF=24
∴AE=2√6
∴AC=√2AE=4√3cm