Description: Lemma for mapdord . (Contributed by NM, 27-Jan-2015)
Ref | Expression | ||
---|---|---|---|
Hypothesis | mapdordlem1.t | |- T = { g e. F | ( O ` ( O ` ( L ` g ) ) ) e. Y } |
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Assertion | mapdordlem1 | |- ( J e. T <-> ( J e. F /\ ( O ` ( O ` ( L ` J ) ) ) e. Y ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | mapdordlem1.t | |- T = { g e. F | ( O ` ( O ` ( L ` g ) ) ) e. Y } |
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2 | 2fveq3 | |- ( g = J -> ( O ` ( L ` g ) ) = ( O ` ( L ` J ) ) ) |
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3 | 2 | fveq2d | |- ( g = J -> ( O ` ( O ` ( L ` g ) ) ) = ( O ` ( O ` ( L ` J ) ) ) ) |
4 | 3 | eleq1d | |- ( g = J -> ( ( O ` ( O ` ( L ` g ) ) ) e. Y <-> ( O ` ( O ` ( L ` J ) ) ) e. Y ) ) |
5 | 4 1 | elrab2 | |- ( J e. T <-> ( J e. F /\ ( O ` ( O ` ( L ` J ) ) ) e. Y ) ) |