As shown in the figure, the trademark o of a certain product is the intersection point of line segments ac and db, and ac=bd, ab=dc. Xiaohua believes that the two triangles in the figure are all
Proof: Link BC
∵AB=DC, AC=DB, BC=CB
∴△ABC≌△DCB (SSS)
∴∠A=∠D
And ∵∠1=∠2 (opposite angles are equal), AB=DC
∴△ABO≌△DCO (AAS)