Description: A virtual deduction elimination rule (see syl6ci ). (Contributed by Alan Sare, 12-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
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Hypotheses | e21.1 | |- (. ph ,. ps ->. ch ). |
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e21.2 | |- (. ph ->. th ). |
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e21.3 | |- ( ch -> ( th -> ta ) ) |
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Assertion | e21 | |- (. ph ,. ps ->. ta ). |
Step | Hyp | Ref | Expression |
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1 | e21.1 | |- (. ph ,. ps ->. ch ). |
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2 | e21.2 | |- (. ph ->. th ). |
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3 | e21.3 | |- ( ch -> ( th -> ta ) ) |
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4 | 2 | vd12 | |- (. ph ,. ps ->. th ). |
5 | 1 4 3 | e22 | |- (. ph ,. ps ->. ta ). |