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ducem DN ⊥ AB
AB = AN + NM + MB
NM = DC = 8 cm
ABCD = isoscel => AN = MB
ΔCMB isoscel dreptunghic (∡ABC = 45°) => MB = CM = 12 cm
AN = MB
MB = 12 cm } => AN = 12 cm
AB = AN + NM + MB = 12 + 8 + 12 = 32 cm