依题意可得：∠BAD = 180°-∠B = 110° ,
∠BAE = ∠BAD-∠EAD = 40° ,
∠AEB = 180°-∠BAE-∠B = 70° .
则有：∠AEB = ∠B ,可得：AE = AB = AD ,
∠AED = (1/2)(180°-∠EAD) = 55° ,
∠DEC = 180°-∠AEB-∠AED = 55° .