Let $K$ be an ordered field with an embedding into $\mathbb R$,
$$f:K\hookrightarrow\mathbb R,$$
where $f$ is order preserving. Is $f$ unique?
Follow up from this question of mine (same question but without ordering assumption). This question is related, but not quite the same.
Yes, in that case it is unique, because for any $x\in K$, its image $f(x)$ is completely characterized by the sets $A=\{a\in \mathbb{Q}|a\leqslant f(x)\}$ and $B=\{b\in \mathbb{Q}|f(x)\leqslant b\}$, and we see that $A=\{a\in \mathbb{Q}|a\leqslant x\}$ and $B=\{b\in \mathbb{Q}|x\leqslant b\}$ so they only depend on the order on $K$.