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<p>then its transitive closure  is a directed set.</p>

<p><big>Product of directed sets</big></p>
<p>Let  and  be directed sets. Then the <a href="page.php?w=Cartesian_product">Cartesian product</a> set  can be made into a directed set by defining  if and only if  and  In analogy to the <a href="page.php?w=product_order">product order</a> this is the product direction on the Cartesian product.  For example, the set  of pairs of natural numbers can be made into a directed set by defining  if and only if  and </p>

<p><big>Directed towards a point</big></p>
<p>If</p><p>
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