Description: Commutative law for restriction and difference. (Contributed by AV, 7-Jun-2021)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | resdifcom | |- ( ( A |` B ) \ C ) = ( ( A \ C ) |` B ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | indif1 | |- ( ( A \ C ) i^i ( B X. _V ) ) = ( ( A i^i ( B X. _V ) ) \ C ) |
|
| 2 | df-res | |- ( ( A \ C ) |` B ) = ( ( A \ C ) i^i ( B X. _V ) ) |
|
| 3 | df-res | |- ( A |` B ) = ( A i^i ( B X. _V ) ) |
|
| 4 | 3 | difeq1i | |- ( ( A |` B ) \ C ) = ( ( A i^i ( B X. _V ) ) \ C ) |
| 5 | 1 2 4 | 3eqtr4ri | |- ( ( A |` B ) \ C ) = ( ( A \ C ) |` B ) |