∴⊿bae≌⊿dac(sas),∠abm=∠adn;
And AB = AD∠BAM=∠DAN=60? .
∴⊿BAM≌⊿DAN(ASA),AM=AN.
(2)∵AM=AN (authentication); ∠MAN= 180? -∠BAD-∠CAE=60? .
∴⊿MAN is an equilateral triangle, ∠AMN=∠MAB=60? .
∴MN∥BC.