Since the lengths of the opposite sides of the parallelogram are equal, then AB = DС, AD = BC.
Then the vector | ↑ DС | = | ↑ AB |.
Vector | ↑ AC | = | ↑ AD | + | ↑ DС |.
Vector | ↑ DВ | = | ↑ DA | + | ↑ AB | = – | ↑ AD | + | ↑ AB | = | ↑ AB | – | ↑ AD |.
Answer: Vector | ↑ AC | = | ↑ AD | + | ↑ DС |, vector | ↑ DВ | = | ↑ AB | – | ↑ AD |.
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