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Theorem 19.9d2rf 29869
 Description: A deduction version of one direction of 19.9 2247 with two variables. (Contributed by Thierry Arnoux, 20-Mar-2017.)
Hypotheses
Ref Expression
19.9d2rf.0 𝑦𝜑
19.9d2rf.1 (𝜑 → Ⅎ𝑥𝜓)
19.9d2rf.2 (𝜑 → Ⅎ𝑦𝜓)
19.9d2rf.3 (𝜑 → ∃𝑥𝐴𝑦𝐵 𝜓)
Assertion
Ref Expression
19.9d2rf (𝜑𝜓)

Proof of Theorem 19.9d2rf
StepHypRef Expression
1 19.9d2rf.3 . . . 4 (𝜑 → ∃𝑥𝐴𝑦𝐵 𝜓)
2 rexex 3210 . . . 4 (∃𝑥𝐴𝑦𝐵 𝜓 → ∃𝑥𝑦𝐵 𝜓)
3 rexex 3210 . . . . 5 (∃𝑦𝐵 𝜓 → ∃𝑦𝜓)
43eximi 1933 . . . 4 (∃𝑥𝑦𝐵 𝜓 → ∃𝑥𝑦𝜓)
51, 2, 43syl 18 . . 3 (𝜑 → ∃𝑥𝑦𝜓)
6 19.9d2rf.0 . . . . 5 𝑦𝜑
7 19.9d2rf.1 . . . . 5 (𝜑 → Ⅎ𝑥𝜓)
86, 7nfexd 2361 . . . 4 (𝜑 → Ⅎ𝑥𝑦𝜓)
9819.9d 2244 . . 3 (𝜑 → (∃𝑥𝑦𝜓 → ∃𝑦𝜓))
105, 9mpd 15 . 2 (𝜑 → ∃𝑦𝜓)
11 19.9d2rf.2 . . 3 (𝜑 → Ⅎ𝑦𝜓)
121119.9d 2244 . 2 (𝜑 → (∃𝑦𝜓𝜓))
1310, 12mpd 15 1 (𝜑𝜓)
 Colors of variables: wff setvar class Syntax hints:   → wi 4  ∃wex 1878  Ⅎwnf 1882  ∃wrex 3118 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1894  ax-4 1908  ax-5 2009  ax-6 2075  ax-7 2112  ax-10 2192  ax-11 2207  ax-12 2220 This theorem depends on definitions:  df-bi 199  df-an 387  df-or 879  df-ex 1879  df-nf 1883  df-rex 3123 This theorem is referenced by:  19.9d2r  29870  xrofsup  30076
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