# Chain is Directed

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## Theorem

Let $\left({S, \preceq}\right)$ be an ordered set.

Let $C$ be a non-empty chain of $S$.

Then $C$ is directed.

## Proof

Let $x, y \in C$.

By definition of connected relation:

- $x \preceq y$ or $y \preceq x$

Without loss of generality, suppose that

- $x \preceq y$

Define $z = y$.

Thus by definition of reflexivity

- $x \preceq z$ and $y \preceq z$

Hence $C$ is directed.

$\blacksquare$

## Sources

- Mizar article WAYBEL_6:condreg 1