Diagonal Relation is Universally Compatible
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Theorem
The diagonal relation $\Delta_S$ on a set $S$ is universally compatible with every operation on $S$.
Proof
Let $\left({S, \circ}\right)$ be any algebraic structure.
\(\displaystyle \) | \(\) | \(\displaystyle x_1 \Delta_S x_2 \land y_1 \Delta_S y_2\) | |||||||||||
\(\displaystyle \) | \(\implies\) | \(\displaystyle x_1 = x_2 \land y_1 = y_2\) | Definition of Diagonal Relation | ||||||||||
\(\displaystyle \) | \(\implies\) | \(\displaystyle x_1 \circ y_1 = x_2 \circ y_2\) | (consequence of equality) | ||||||||||
\(\displaystyle \) | \(\implies\) | \(\displaystyle \left({x_1 \circ y_1}\right) \Delta_S \left({x_2 \circ y_2}\right)\) | Definition of Diagonal Relation |
$\blacksquare$