第3题证明:∵∠BAE = ∠CAD(公尺和共角),且已知∠B = ∠C,AE = AD,∴△ABE ≌ △ACD (AAS)探索三角形全等条件(5)第唤困好1题证明:∵ B是EC的中点∴EB = BC∵和铅 ∠ABC = 180° - ∠ABE ,∠DBE = 180° - ∠DBC又∵ ∠ABE = ∠DBC∴ ∠ABC = ∠DBE又已知 ∠A = ∠D∴ △ABC ≌ △DBE (AAS)∴ DE = AC
用sas