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Description: A diagonal set as a subset of a Cartesian square. (Contributed by Thierry Arnoux, 29-Dec-2019) (Proof shortened by BJ, 9-Sep-2022)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | idssxp |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | idinxpresid | ||
| 2 | inss2 | ||
| 3 | 1 2 | eqsstrri |