如图，△ABC全等于△A'B'C',AD、A'D'分别是△ABC与△A'B'C'的中线.求证：AD=A'D'.

∵?ABC≌?A′B′C′ ∴∠B=∠B′,∠A=∠A′,AB=A′B′ ∵AD,A′D′分别平分∠BAC,∠B′A′C′ ∴∠BAD=∠B′A′D′ ∴∠B=∠B′,AB=A′B′,∠BAD=∠B′A′D′ ∴?BAD≌?B′A′D′ ∴AD=A′D′