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Description: The modulo function I is idempotent. (Contributed by AV, 12-Feb-2024)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | smndex1ibas.m | |- M = ( EndoFMnd ` NN0 ) |
|
| smndex1ibas.n | |- N e. NN |
||
| smndex1ibas.i | |- I = ( x e. NN0 |-> ( x mod N ) ) |
||
| Assertion | smndex1iidm | |- ( I o. I ) = I |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | smndex1ibas.m | |- M = ( EndoFMnd ` NN0 ) |
|
| 2 | smndex1ibas.n | |- N e. NN |
|
| 3 | smndex1ibas.i | |- I = ( x e. NN0 |-> ( x mod N ) ) |
|
| 4 | nn0re | |- ( y e. NN0 -> y e. RR ) |
|
| 5 | nnrp | |- ( N e. NN -> N e. RR+ ) |
|
| 6 | 2 5 | ax-mp | |- N e. RR+ |
| 7 | modabs2 | |- ( ( y e. RR /\ N e. RR+ ) -> ( ( y mod N ) mod N ) = ( y mod N ) ) |
|
| 8 | 4 6 7 | sylancl | |- ( y e. NN0 -> ( ( y mod N ) mod N ) = ( y mod N ) ) |
| 9 | 8 | eqcomd | |- ( y e. NN0 -> ( y mod N ) = ( ( y mod N ) mod N ) ) |
| 10 | 9 | mpteq2ia | |- ( y e. NN0 |-> ( y mod N ) ) = ( y e. NN0 |-> ( ( y mod N ) mod N ) ) |
| 11 | oveq1 | |- ( x = y -> ( x mod N ) = ( y mod N ) ) |
|
| 12 | 11 | cbvmptv | |- ( x e. NN0 |-> ( x mod N ) ) = ( y e. NN0 |-> ( y mod N ) ) |
| 13 | 3 12 | eqtri | |- I = ( y e. NN0 |-> ( y mod N ) ) |
| 14 | nn0z | |- ( y e. NN0 -> y e. ZZ ) |
|
| 15 | 14 | anim2i | |- ( ( N e. NN /\ y e. NN0 ) -> ( N e. NN /\ y e. ZZ ) ) |
| 16 | 15 | ancomd | |- ( ( N e. NN /\ y e. NN0 ) -> ( y e. ZZ /\ N e. NN ) ) |
| 17 | zmodcl | |- ( ( y e. ZZ /\ N e. NN ) -> ( y mod N ) e. NN0 ) |
|
| 18 | 16 17 | syl | |- ( ( N e. NN /\ y e. NN0 ) -> ( y mod N ) e. NN0 ) |
| 19 | 13 | a1i | |- ( N e. NN -> I = ( y e. NN0 |-> ( y mod N ) ) ) |
| 20 | 3 | a1i | |- ( N e. NN -> I = ( x e. NN0 |-> ( x mod N ) ) ) |
| 21 | oveq1 | |- ( x = ( y mod N ) -> ( x mod N ) = ( ( y mod N ) mod N ) ) |
|
| 22 | 18 19 20 21 | fmptco | |- ( N e. NN -> ( I o. I ) = ( y e. NN0 |-> ( ( y mod N ) mod N ) ) ) |
| 23 | 2 22 | ax-mp | |- ( I o. I ) = ( y e. NN0 |-> ( ( y mod N ) mod N ) ) |
| 24 | 10 13 23 | 3eqtr4ri | |- ( I o. I ) = I |