Question

如图,AD=BC,AC=BD.求证；（1）∠DAB=∠CBA.(2)∠ACD=∠BDC

Answer 1

①证明:∵AD＝BC,AC＝BD ∴在△ABD和△BAC中

{AD＝BC

{AC＝BD

{AB＝AB ∴△ABD≌

△BAC

∴∠DAB＝∠CBA

②证明:∵AD＝BC,AC＝BD ∴在△ADC和△BCD中

{AD＝BC

{AC＝BD

{DC＝DC

∴△ADC≌

△BCD

∴∠ACD＝∠BDC