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Description: Induction in a monoid. In this theorem, ps ( x ) is the "generic" proposition to be be proved (the first four hypotheses tell its values at y, y+z, 0, A respectively). The two induction hypotheses mndind.i1 and mndind.i2 tell that it is true at 0, that if it is true at y then it is true at y+z (provided z is in G ). The hypothesis mndind.k tells that G is generating. (Contributed by SO, 14-Jul-2018)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | mndind.ch | |- ( x = y -> ( ps <-> ch ) ) |
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| mndind.th | |- ( x = ( y .+ z ) -> ( ps <-> th ) ) |
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| mndind.ta | |- ( x = .0. -> ( ps <-> ta ) ) |
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| mndind.et | |- ( x = A -> ( ps <-> et ) ) |
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| mndind.0g | |- .0. = ( 0g ` M ) |
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| mndind.pg | |- .+ = ( +g ` M ) |
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| mndind.b | |- B = ( Base ` M ) |
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| mndind.m | |- ( ph -> M e. Mnd ) |
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| mndind.g | |- ( ph -> G C_ B ) |
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| mndind.k | |- ( ph -> B = ( ( mrCls ` ( SubMnd ` M ) ) ` G ) ) |
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| mndind.i1 | |- ( ph -> ta ) |
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| mndind.i2 | |- ( ( ( ph /\ y e. B /\ z e. G ) /\ ch ) -> th ) |
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| mndind.a | |- ( ph -> A e. B ) |
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| Assertion | mndind | |- ( ph -> et ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | mndind.ch | |- ( x = y -> ( ps <-> ch ) ) |
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| 2 | mndind.th | |- ( x = ( y .+ z ) -> ( ps <-> th ) ) |
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| 3 | mndind.ta | |- ( x = .0. -> ( ps <-> ta ) ) |
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| 4 | mndind.et | |- ( x = A -> ( ps <-> et ) ) |
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| 5 | mndind.0g | |- .0. = ( 0g ` M ) |
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| 6 | mndind.pg | |- .+ = ( +g ` M ) |
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| 7 | mndind.b | |- B = ( Base ` M ) |
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| 8 | mndind.m | |- ( ph -> M e. Mnd ) |
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| 9 | mndind.g | |- ( ph -> G C_ B ) |
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| 10 | mndind.k | |- ( ph -> B = ( ( mrCls ` ( SubMnd ` M ) ) ` G ) ) |
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| 11 | mndind.i1 | |- ( ph -> ta ) |
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| 12 | mndind.i2 | |- ( ( ( ph /\ y e. B /\ z e. G ) /\ ch ) -> th ) |
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| 13 | mndind.a | |- ( ph -> A e. B ) |
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| 14 | 7 5 | mndidcl | |- ( M e. Mnd -> .0. e. B ) |
| 15 | 8 14 | syl | |- ( ph -> .0. e. B ) |
| 16 | 3 | sbcieg | |- ( .0. e. B -> ( [. .0. / x ]. ps <-> ta ) ) |
| 17 | 15 16 | syl | |- ( ph -> ( [. .0. / x ]. ps <-> ta ) ) |
| 18 | 11 17 | mpbird | |- ( ph -> [. .0. / x ]. ps ) |
| 19 | dfsbcq | |- ( a = .0. -> ( [. a / x ]. ps <-> [. .0. / x ]. ps ) ) |
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| 20 | oveq1 | |- ( a = .0. -> ( a .+ A ) = ( .0. .+ A ) ) |
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| 21 | 20 | sbceq1d | |- ( a = .0. -> ( [. ( a .+ A ) / x ]. ps <-> [. ( .0. .+ A ) / x ]. ps ) ) |
| 22 | 19 21 | imbi12d | |- ( a = .0. -> ( ( [. a / x ]. ps -> [. ( a .+ A ) / x ]. ps ) <-> ( [. .0. / x ]. ps -> [. ( .0. .+ A ) / x ]. ps ) ) ) |
| 23 | 7 | submacs | |- ( M e. Mnd -> ( SubMnd ` M ) e. ( ACS ` B ) ) |
| 24 | 8 23 | syl | |- ( ph -> ( SubMnd ` M ) e. ( ACS ` B ) ) |
| 25 | 24 | acsmred | |- ( ph -> ( SubMnd ` M ) e. ( Moore ` B ) ) |
| 26 | eleq1w | |- ( y = a -> ( y e. B <-> a e. B ) ) |
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| 27 | 26 | anbi2d | |- ( y = a -> ( ( ( ph /\ b e. G ) /\ y e. B ) <-> ( ( ph /\ b e. G ) /\ a e. B ) ) ) |
| 28 | vex | |- y e. _V |
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| 29 | 28 1 | sbcie | |- ( [. y / x ]. ps <-> ch ) |
| 30 | dfsbcq | |- ( y = a -> ( [. y / x ]. ps <-> [. a / x ]. ps ) ) |
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| 31 | 29 30 | bitr3id | |- ( y = a -> ( ch <-> [. a / x ]. ps ) ) |
| 32 | oveq1 | |- ( y = a -> ( y .+ b ) = ( a .+ b ) ) |
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| 33 | 32 | sbceq1d | |- ( y = a -> ( [. ( y .+ b ) / x ]. ps <-> [. ( a .+ b ) / x ]. ps ) ) |
| 34 | 31 33 | imbi12d | |- ( y = a -> ( ( ch -> [. ( y .+ b ) / x ]. ps ) <-> ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) ) ) |
| 35 | 27 34 | imbi12d | |- ( y = a -> ( ( ( ( ph /\ b e. G ) /\ y e. B ) -> ( ch -> [. ( y .+ b ) / x ]. ps ) ) <-> ( ( ( ph /\ b e. G ) /\ a e. B ) -> ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) ) ) ) |
| 36 | eleq1w | |- ( z = b -> ( z e. G <-> b e. G ) ) |
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| 37 | 36 | anbi2d | |- ( z = b -> ( ( ph /\ z e. G ) <-> ( ph /\ b e. G ) ) ) |
| 38 | 37 | anbi1d | |- ( z = b -> ( ( ( ph /\ z e. G ) /\ y e. B ) <-> ( ( ph /\ b e. G ) /\ y e. B ) ) ) |
| 39 | ovex | |- ( y .+ z ) e. _V |
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| 40 | 39 2 | sbcie | |- ( [. ( y .+ z ) / x ]. ps <-> th ) |
| 41 | oveq2 | |- ( z = b -> ( y .+ z ) = ( y .+ b ) ) |
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| 42 | 41 | sbceq1d | |- ( z = b -> ( [. ( y .+ z ) / x ]. ps <-> [. ( y .+ b ) / x ]. ps ) ) |
| 43 | 40 42 | bitr3id | |- ( z = b -> ( th <-> [. ( y .+ b ) / x ]. ps ) ) |
| 44 | 43 | imbi2d | |- ( z = b -> ( ( ch -> th ) <-> ( ch -> [. ( y .+ b ) / x ]. ps ) ) ) |
| 45 | 38 44 | imbi12d | |- ( z = b -> ( ( ( ( ph /\ z e. G ) /\ y e. B ) -> ( ch -> th ) ) <-> ( ( ( ph /\ b e. G ) /\ y e. B ) -> ( ch -> [. ( y .+ b ) / x ]. ps ) ) ) ) |
| 46 | 12 | ex | |- ( ( ph /\ y e. B /\ z e. G ) -> ( ch -> th ) ) |
| 47 | 46 | 3expa | |- ( ( ( ph /\ y e. B ) /\ z e. G ) -> ( ch -> th ) ) |
| 48 | 47 | an32s | |- ( ( ( ph /\ z e. G ) /\ y e. B ) -> ( ch -> th ) ) |
| 49 | 45 48 | chvarvv | |- ( ( ( ph /\ b e. G ) /\ y e. B ) -> ( ch -> [. ( y .+ b ) / x ]. ps ) ) |
| 50 | 35 49 | chvarvv | |- ( ( ( ph /\ b e. G ) /\ a e. B ) -> ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) ) |
| 51 | 50 | ralrimiva | |- ( ( ph /\ b e. G ) -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) ) |
| 52 | 9 51 | ssrabdv | |- ( ph -> G C_ { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } ) |
| 53 | 7 6 5 | mndrid | |- ( ( M e. Mnd /\ a e. B ) -> ( a .+ .0. ) = a ) |
| 54 | 8 53 | sylan | |- ( ( ph /\ a e. B ) -> ( a .+ .0. ) = a ) |
| 55 | 54 | sbceq1d | |- ( ( ph /\ a e. B ) -> ( [. ( a .+ .0. ) / x ]. ps <-> [. a / x ]. ps ) ) |
| 56 | 55 | biimprd | |- ( ( ph /\ a e. B ) -> ( [. a / x ]. ps -> [. ( a .+ .0. ) / x ]. ps ) ) |
| 57 | 56 | ralrimiva | |- ( ph -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ .0. ) / x ]. ps ) ) |
| 58 | simprrl | |- ( ( ph /\ ( ( c e. B /\ d e. B ) /\ ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) /\ A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) ) -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) ) |
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| 59 | 8 | ad2antrr | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> M e. Mnd ) |
| 60 | simpr | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> b e. B ) |
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| 61 | simplrl | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> c e. B ) |
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| 62 | 7 6 | mndcl | |- ( ( M e. Mnd /\ b e. B /\ c e. B ) -> ( b .+ c ) e. B ) |
| 63 | 59 60 61 62 | syl3anc | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> ( b .+ c ) e. B ) |
| 64 | simpr | |- ( ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) /\ a = ( b .+ c ) ) -> a = ( b .+ c ) ) |
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| 65 | 64 | sbceq1d | |- ( ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) /\ a = ( b .+ c ) ) -> ( [. a / x ]. ps <-> [. ( b .+ c ) / x ]. ps ) ) |
| 66 | oveq1 | |- ( a = ( b .+ c ) -> ( a .+ d ) = ( ( b .+ c ) .+ d ) ) |
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| 67 | simplrr | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> d e. B ) |
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| 68 | 7 6 | mndass | |- ( ( M e. Mnd /\ ( b e. B /\ c e. B /\ d e. B ) ) -> ( ( b .+ c ) .+ d ) = ( b .+ ( c .+ d ) ) ) |
| 69 | 59 60 61 67 68 | syl13anc | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> ( ( b .+ c ) .+ d ) = ( b .+ ( c .+ d ) ) ) |
| 70 | 66 69 | sylan9eqr | |- ( ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) /\ a = ( b .+ c ) ) -> ( a .+ d ) = ( b .+ ( c .+ d ) ) ) |
| 71 | 70 | sbceq1d | |- ( ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) /\ a = ( b .+ c ) ) -> ( [. ( a .+ d ) / x ]. ps <-> [. ( b .+ ( c .+ d ) ) / x ]. ps ) ) |
| 72 | 65 71 | imbi12d | |- ( ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) /\ a = ( b .+ c ) ) -> ( ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) <-> ( [. ( b .+ c ) / x ]. ps -> [. ( b .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 73 | 63 72 | rspcdv | |- ( ( ( ph /\ ( c e. B /\ d e. B ) ) /\ b e. B ) -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) -> ( [. ( b .+ c ) / x ]. ps -> [. ( b .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 74 | 73 | ralrimdva | |- ( ( ph /\ ( c e. B /\ d e. B ) ) -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) -> A. b e. B ( [. ( b .+ c ) / x ]. ps -> [. ( b .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 75 | 74 | impr | |- ( ( ph /\ ( ( c e. B /\ d e. B ) /\ A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) -> A. b e. B ( [. ( b .+ c ) / x ]. ps -> [. ( b .+ ( c .+ d ) ) / x ]. ps ) ) |
| 76 | oveq1 | |- ( b = a -> ( b .+ c ) = ( a .+ c ) ) |
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| 77 | 76 | sbceq1d | |- ( b = a -> ( [. ( b .+ c ) / x ]. ps <-> [. ( a .+ c ) / x ]. ps ) ) |
| 78 | oveq1 | |- ( b = a -> ( b .+ ( c .+ d ) ) = ( a .+ ( c .+ d ) ) ) |
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| 79 | 78 | sbceq1d | |- ( b = a -> ( [. ( b .+ ( c .+ d ) ) / x ]. ps <-> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) |
| 80 | 77 79 | imbi12d | |- ( b = a -> ( ( [. ( b .+ c ) / x ]. ps -> [. ( b .+ ( c .+ d ) ) / x ]. ps ) <-> ( [. ( a .+ c ) / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 81 | 80 | cbvralvw | |- ( A. b e. B ( [. ( b .+ c ) / x ]. ps -> [. ( b .+ ( c .+ d ) ) / x ]. ps ) <-> A. a e. B ( [. ( a .+ c ) / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) |
| 82 | 75 81 | sylib | |- ( ( ph /\ ( ( c e. B /\ d e. B ) /\ A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) -> A. a e. B ( [. ( a .+ c ) / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) |
| 83 | 82 | adantrrl | |- ( ( ph /\ ( ( c e. B /\ d e. B ) /\ ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) /\ A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) ) -> A. a e. B ( [. ( a .+ c ) / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) |
| 84 | imim1 | |- ( ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) -> ( ( [. ( a .+ c ) / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) -> ( [. a / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) ) |
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| 85 | 84 | ral2imi | |- ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) -> ( A. a e. B ( [. ( a .+ c ) / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 86 | 58 83 85 | sylc | |- ( ( ph /\ ( ( c e. B /\ d e. B ) /\ ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) /\ A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) ) -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) |
| 87 | oveq2 | |- ( b = .0. -> ( a .+ b ) = ( a .+ .0. ) ) |
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| 88 | 87 | sbceq1d | |- ( b = .0. -> ( [. ( a .+ b ) / x ]. ps <-> [. ( a .+ .0. ) / x ]. ps ) ) |
| 89 | 88 | imbi2d | |- ( b = .0. -> ( ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> ( [. a / x ]. ps -> [. ( a .+ .0. ) / x ]. ps ) ) ) |
| 90 | 89 | ralbidv | |- ( b = .0. -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> A. a e. B ( [. a / x ]. ps -> [. ( a .+ .0. ) / x ]. ps ) ) ) |
| 91 | oveq2 | |- ( b = c -> ( a .+ b ) = ( a .+ c ) ) |
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| 92 | 91 | sbceq1d | |- ( b = c -> ( [. ( a .+ b ) / x ]. ps <-> [. ( a .+ c ) / x ]. ps ) ) |
| 93 | 92 | imbi2d | |- ( b = c -> ( ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) ) ) |
| 94 | 93 | ralbidv | |- ( b = c -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> A. a e. B ( [. a / x ]. ps -> [. ( a .+ c ) / x ]. ps ) ) ) |
| 95 | oveq2 | |- ( b = d -> ( a .+ b ) = ( a .+ d ) ) |
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| 96 | 95 | sbceq1d | |- ( b = d -> ( [. ( a .+ b ) / x ]. ps <-> [. ( a .+ d ) / x ]. ps ) ) |
| 97 | 96 | imbi2d | |- ( b = d -> ( ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) |
| 98 | 97 | ralbidv | |- ( b = d -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> A. a e. B ( [. a / x ]. ps -> [. ( a .+ d ) / x ]. ps ) ) ) |
| 99 | oveq2 | |- ( b = ( c .+ d ) -> ( a .+ b ) = ( a .+ ( c .+ d ) ) ) |
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| 100 | 99 | sbceq1d | |- ( b = ( c .+ d ) -> ( [. ( a .+ b ) / x ]. ps <-> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) |
| 101 | 100 | imbi2d | |- ( b = ( c .+ d ) -> ( ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> ( [. a / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 102 | 101 | ralbidv | |- ( b = ( c .+ d ) -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> A. a e. B ( [. a / x ]. ps -> [. ( a .+ ( c .+ d ) ) / x ]. ps ) ) ) |
| 103 | 7 6 5 8 57 86 90 94 98 102 | issubmd | |- ( ph -> { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } e. ( SubMnd ` M ) ) |
| 104 | eqid | |- ( mrCls ` ( SubMnd ` M ) ) = ( mrCls ` ( SubMnd ` M ) ) |
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| 105 | 104 | mrcsscl | |- ( ( ( SubMnd ` M ) e. ( Moore ` B ) /\ G C_ { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } /\ { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } e. ( SubMnd ` M ) ) -> ( ( mrCls ` ( SubMnd ` M ) ) ` G ) C_ { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } ) |
| 106 | 25 52 103 105 | syl3anc | |- ( ph -> ( ( mrCls ` ( SubMnd ` M ) ) ` G ) C_ { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } ) |
| 107 | 10 106 | eqsstrd | |- ( ph -> B C_ { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } ) |
| 108 | 107 13 | sseldd | |- ( ph -> A e. { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } ) |
| 109 | oveq2 | |- ( b = A -> ( a .+ b ) = ( a .+ A ) ) |
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| 110 | 109 | sbceq1d | |- ( b = A -> ( [. ( a .+ b ) / x ]. ps <-> [. ( a .+ A ) / x ]. ps ) ) |
| 111 | 110 | imbi2d | |- ( b = A -> ( ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> ( [. a / x ]. ps -> [. ( a .+ A ) / x ]. ps ) ) ) |
| 112 | 111 | ralbidv | |- ( b = A -> ( A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) <-> A. a e. B ( [. a / x ]. ps -> [. ( a .+ A ) / x ]. ps ) ) ) |
| 113 | 112 | elrab | |- ( A e. { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } <-> ( A e. B /\ A. a e. B ( [. a / x ]. ps -> [. ( a .+ A ) / x ]. ps ) ) ) |
| 114 | 113 | simprbi | |- ( A e. { b e. B | A. a e. B ( [. a / x ]. ps -> [. ( a .+ b ) / x ]. ps ) } -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ A ) / x ]. ps ) ) |
| 115 | 108 114 | syl | |- ( ph -> A. a e. B ( [. a / x ]. ps -> [. ( a .+ A ) / x ]. ps ) ) |
| 116 | 22 115 15 | rspcdva | |- ( ph -> ( [. .0. / x ]. ps -> [. ( .0. .+ A ) / x ]. ps ) ) |
| 117 | 18 116 | mpd | |- ( ph -> [. ( .0. .+ A ) / x ]. ps ) |
| 118 | 7 6 5 | mndlid | |- ( ( M e. Mnd /\ A e. B ) -> ( .0. .+ A ) = A ) |
| 119 | 8 13 118 | syl2anc | |- ( ph -> ( .0. .+ A ) = A ) |
| 120 | 119 | sbceq1d | |- ( ph -> ( [. ( .0. .+ A ) / x ]. ps <-> [. A / x ]. ps ) ) |
| 121 | 4 | sbcieg | |- ( A e. B -> ( [. A / x ]. ps <-> et ) ) |
| 122 | 13 121 | syl | |- ( ph -> ( [. A / x ]. ps <-> et ) ) |
| 123 | 120 122 | bitrd | |- ( ph -> ( [. ( .0. .+ A ) / x ]. ps <-> et ) ) |
| 124 | 117 123 | mpbid | |- ( ph -> et ) |