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Description: A virtual deduction elimination rule. (Contributed by Alan Sare, 12-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | e222.1 | |- (. ph ,. ps ->. ch ). |
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| e222.2 | |- (. ph ,. ps ->. th ). |
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| e222.3 | |- (. ph ,. ps ->. ta ). |
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| e222.4 | |- ( ch -> ( th -> ( ta -> et ) ) ) |
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| Assertion | e222 | |- (. ph ,. ps ->. et ). |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | e222.1 | |- (. ph ,. ps ->. ch ). |
|
| 2 | e222.2 | |- (. ph ,. ps ->. th ). |
|
| 3 | e222.3 | |- (. ph ,. ps ->. ta ). |
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| 4 | e222.4 | |- ( ch -> ( th -> ( ta -> et ) ) ) |
|
| 5 | 3 | dfvd2i | |- ( ph -> ( ps -> ta ) ) |
| 6 | 5 | imp | |- ( ( ph /\ ps ) -> ta ) |
| 7 | 1 | dfvd2i | |- ( ph -> ( ps -> ch ) ) |
| 8 | 7 | imp | |- ( ( ph /\ ps ) -> ch ) |
| 9 | 2 | dfvd2i | |- ( ph -> ( ps -> th ) ) |
| 10 | 9 | imp | |- ( ( ph /\ ps ) -> th ) |
| 11 | 8 10 4 | syl2im | |- ( ( ph /\ ps ) -> ( ( ph /\ ps ) -> ( ta -> et ) ) ) |
| 12 | 11 | pm2.43i | |- ( ( ph /\ ps ) -> ( ta -> et ) ) |
| 13 | 6 12 | syl5com | |- ( ( ph /\ ps ) -> ( ( ph /\ ps ) -> et ) ) |
| 14 | 13 | pm2.43i | |- ( ( ph /\ ps ) -> et ) |
| 15 | 14 | ex | |- ( ph -> ( ps -> et ) ) |
| 16 | 15 | dfvd2ir | |- (. ph ,. ps ->. et ). |