It is known that, as shown in the figure, ∠ ABC = ∠ DCB, BD and Ca are bisectors of ∠ ABC and ∠ DCB respectively

It is known that, as shown in the figure, ∠ ABC = ∠ DCB, BD and Ca are bisectors of ∠ ABC and ∠ DCB respectively

It is proved that: ∵ AC bisection ∵ BCD, BD bisection ∵ ABC, ∵ DBC = 12 ∵ ABC, ∵ ACB = 12 ∵ DCB, ∵ ABC = ≌ DCB, ∵ AB = DC