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Theorem xmulf 12307
Description: The extended real multiplication operation is closed in extended reals. (Contributed by Mario Carneiro, 21-Aug-2015.)
Assertion
Ref Expression
xmulf ·e :(ℝ* × ℝ*)⟶ℝ*

Proof of Theorem xmulf
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 0xr 10288 . . . . 5 0 ∈ ℝ*
21a1i 11 . . . 4 (((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ (𝑥 = 0 ∨ 𝑦 = 0)) → 0 ∈ ℝ*)
3 pnfxr 10294 . . . . . 6 +∞ ∈ ℝ*
43a1i 11 . . . . 5 ((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) → +∞ ∈ ℝ*)
5 mnfxr 10298 . . . . . . 7 -∞ ∈ ℝ*
65a1i 11 . . . . . 6 (((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) ∧ (((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)))) → -∞ ∈ ℝ*)
7 xmullem 12299 . . . . . . . 8 (((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) ∧ ¬ (((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)))) → 𝑥 ∈ ℝ)
8 ancom 452 . . . . . . . . . . 11 ((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ↔ (𝑦 ∈ ℝ*𝑥 ∈ ℝ*))
9 orcom 849 . . . . . . . . . . . 12 ((𝑥 = 0 ∨ 𝑦 = 0) ↔ (𝑦 = 0 ∨ 𝑥 = 0))
109notbii 309 . . . . . . . . . . 11 (¬ (𝑥 = 0 ∨ 𝑦 = 0) ↔ ¬ (𝑦 = 0 ∨ 𝑥 = 0))
118, 10anbi12i 604 . . . . . . . . . 10 (((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ↔ ((𝑦 ∈ ℝ*𝑥 ∈ ℝ*) ∧ ¬ (𝑦 = 0 ∨ 𝑥 = 0)))
12 orcom 849 . . . . . . . . . . 11 ((((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))) ↔ (((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)) ∨ ((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞))))
1312notbii 309 . . . . . . . . . 10 (¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))) ↔ ¬ (((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)) ∨ ((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞))))
1411, 13anbi12i 604 . . . . . . . . 9 ((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) ↔ (((𝑦 ∈ ℝ*𝑥 ∈ ℝ*) ∧ ¬ (𝑦 = 0 ∨ 𝑥 = 0)) ∧ ¬ (((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)) ∨ ((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)))))
15 orcom 849 . . . . . . . . . 10 ((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))) ↔ (((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)) ∨ ((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞))))
1615notbii 309 . . . . . . . . 9 (¬ (((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))) ↔ ¬ (((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)) ∨ ((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞))))
17 xmullem 12299 . . . . . . . . 9 (((((𝑦 ∈ ℝ*𝑥 ∈ ℝ*) ∧ ¬ (𝑦 = 0 ∨ 𝑥 = 0)) ∧ ¬ (((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)) ∨ ((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)))) ∧ ¬ (((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)) ∨ ((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)))) → 𝑦 ∈ ℝ)
1814, 16, 17syl2anb 577 . . . . . . . 8 (((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) ∧ ¬ (((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)))) → 𝑦 ∈ ℝ)
197, 18remulcld 10272 . . . . . . 7 (((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) ∧ ¬ (((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)))) → (𝑥 · 𝑦) ∈ ℝ)
2019rexrd 10291 . . . . . 6 (((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) ∧ ¬ (((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞)))) → (𝑥 · 𝑦) ∈ ℝ*)
216, 20ifclda 4259 . . . . 5 ((((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) ∧ ¬ (((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞)))) → if((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))), -∞, (𝑥 · 𝑦)) ∈ ℝ*)
224, 21ifclda 4259 . . . 4 (((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) ∧ ¬ (𝑥 = 0 ∨ 𝑦 = 0)) → if((((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))), +∞, if((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))), -∞, (𝑥 · 𝑦))) ∈ ℝ*)
232, 22ifclda 4259 . . 3 ((𝑥 ∈ ℝ*𝑦 ∈ ℝ*) → if((𝑥 = 0 ∨ 𝑦 = 0), 0, if((((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))), +∞, if((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))), -∞, (𝑥 · 𝑦)))) ∈ ℝ*)
2423rgen2a 3126 . 2 𝑥 ∈ ℝ*𝑦 ∈ ℝ* if((𝑥 = 0 ∨ 𝑦 = 0), 0, if((((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))), +∞, if((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))), -∞, (𝑥 · 𝑦)))) ∈ ℝ*
25 df-xmul 12153 . . 3 ·e = (𝑥 ∈ ℝ*, 𝑦 ∈ ℝ* ↦ if((𝑥 = 0 ∨ 𝑦 = 0), 0, if((((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))), +∞, if((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))), -∞, (𝑥 · 𝑦)))))
2625fmpt2 7387 . 2 (∀𝑥 ∈ ℝ*𝑦 ∈ ℝ* if((𝑥 = 0 ∨ 𝑦 = 0), 0, if((((0 < 𝑦𝑥 = +∞) ∨ (𝑦 < 0 ∧ 𝑥 = -∞)) ∨ ((0 < 𝑥𝑦 = +∞) ∨ (𝑥 < 0 ∧ 𝑦 = -∞))), +∞, if((((0 < 𝑦𝑥 = -∞) ∨ (𝑦 < 0 ∧ 𝑥 = +∞)) ∨ ((0 < 𝑥𝑦 = -∞) ∨ (𝑥 < 0 ∧ 𝑦 = +∞))), -∞, (𝑥 · 𝑦)))) ∈ ℝ* ↔ ·e :(ℝ* × ℝ*)⟶ℝ*)
2724, 26mpbi 220 1 ·e :(ℝ* × ℝ*)⟶ℝ*
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wa 382  wo 826   = wceq 1631  wcel 2145  wral 3061  ifcif 4225   class class class wbr 4786   × cxp 5247  wf 6027  (class class class)co 6793  cr 10137  0cc0 10138   · cmul 10143  +∞cpnf 10273  -∞cmnf 10274  *cxr 10275   < clt 10276   ·e cxmu 12150
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1870  ax-4 1885  ax-5 1991  ax-6 2057  ax-7 2093  ax-8 2147  ax-9 2154  ax-10 2174  ax-11 2190  ax-12 2203  ax-13 2408  ax-ext 2751  ax-sep 4915  ax-nul 4923  ax-pow 4974  ax-pr 5034  ax-un 7096  ax-cnex 10194  ax-resscn 10195  ax-1cn 10196  ax-icn 10197  ax-addcl 10198  ax-addrcl 10199  ax-mulcl 10200  ax-mulrcl 10201  ax-i2m1 10206  ax-1ne0 10207  ax-rnegex 10209  ax-rrecex 10210  ax-cnre 10211  ax-pre-lttri 10212  ax-pre-lttrn 10213
This theorem depends on definitions:  df-bi 197  df-an 383  df-or 827  df-3or 1072  df-3an 1073  df-tru 1634  df-ex 1853  df-nf 1858  df-sb 2050  df-eu 2622  df-mo 2623  df-clab 2758  df-cleq 2764  df-clel 2767  df-nfc 2902  df-ne 2944  df-nel 3047  df-ral 3066  df-rex 3067  df-rab 3070  df-v 3353  df-sbc 3588  df-csb 3683  df-dif 3726  df-un 3728  df-in 3730  df-ss 3737  df-nul 4064  df-if 4226  df-pw 4299  df-sn 4317  df-pr 4319  df-op 4323  df-uni 4575  df-iun 4656  df-br 4787  df-opab 4847  df-mpt 4864  df-id 5157  df-po 5170  df-so 5171  df-xp 5255  df-rel 5256  df-cnv 5257  df-co 5258  df-dm 5259  df-rn 5260  df-res 5261  df-ima 5262  df-iota 5994  df-fun 6033  df-fn 6034  df-f 6035  df-f1 6036  df-fo 6037  df-f1o 6038  df-fv 6039  df-ov 6796  df-oprab 6797  df-mpt2 6798  df-1st 7315  df-2nd 7316  df-er 7896  df-en 8110  df-dom 8111  df-sdom 8112  df-pnf 10278  df-mnf 10279  df-xr 10280  df-ltxr 10281  df-xmul 12153
This theorem is referenced by:  xmulcl  12308  xrsmul  19979
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