Theorem ersymb 5954

Description: An equivalence relation is symmetric. (Contributed by set.mm contributors, 30-Jul-1995.) (Revised by set.mm contributors, 9-Jul-2014.)

Hypotheses

Ref	Expression
ersymb.1	|- (ph -> R Er A)
ersymb.2	|- (ph -> X e. A)
ersymb.3	|- (ph -> Y e. A)

Assertion

Ref	Expression
ersymb	|- (ph -> (XRY <-> YRX))

Proof of Theorem ersymb

Step	Hyp	Ref	Expression
1		ersymb.1	. . . 4 |- (ph -> R Er A)
2	1	adantr 451	. . 3 |- ((ph /\ XRY) -> R Er A)
3		ersymb.2	. . . 4 |- (ph -> X e. A)
4	3	adantr 451	. . 3 |- ((ph /\ XRY) -> X e. A)
5		ersymb.3	. . . 4 |- (ph -> Y e. A)
6	5	adantr 451	. . 3 |- ((ph /\ XRY) -> Y e. A)
7		simpr 447	. . 3 |- ((ph /\ XRY) -> XRY)
8	2, 4, 6, 7	ersym 5953	. 2 |- ((ph /\ XRY) -> YRX)
9	1	adantr 451	. . 3 |- ((ph /\ YRX) -> R Er A)
10	5	adantr 451	. . 3 |- ((ph /\ YRX) -> Y e. A)
11	3	adantr 451	. . 3 |- ((ph /\ YRX) -> X e. A)
12		simpr 447	. . 3 |- ((ph /\ YRX) -> YRX)
13	9, 10, 11, 12	ersym 5953	. 2 |- ((ph /\ YRX) -> XRY)
14	8, 13	impbida 805	1 |- (ph -> (XRY <-> YRX))

Syntax hints:   -> wi 4   <-> wb 176   /\ wa 358   e. wcel 1710   class class class wbr 4640   Er cer 5899

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-13 1712  ax-14 1714  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334  ax-nin 4079  ax-xp 4080  ax-cnv 4081  ax-1c 4082  ax-sset 4083  ax-si 4084  ax-ins2 4085  ax-ins3 4086  ax-typlower 4087  ax-sn 4088

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-3or 935  df-3an 936  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-eu 2208  df-mo 2209  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2479  df-ne 2519  df-ral 2620  df-rex 2621  df-reu 2622  df-rmo 2623  df-rab 2624  df-v 2862  df-sbc 3048  df-nin 3212  df-compl 3213  df-in 3214  df-un 3215  df-dif 3216  df-symdif 3217  df-ss 3260  df-pss 3262  df-nul 3552  df-if 3664  df-pw 3725  df-sn 3742  df-pr 3743  df-uni 3893  df-int 3928  df-opk 4059  df-1c 4137  df-pw1 4138  df-uni1 4139  df-xpk 4186  df-cnvk 4187  df-ins2k 4188  df-ins3k 4189  df-imak 4190  df-cok 4191  df-p6 4192  df-sik 4193  df-ssetk 4194  df-imagek 4195  df-idk 4196  df-iota 4340  df-0c 4378  df-addc 4379  df-nnc 4380  df-fin 4381  df-lefin 4441  df-ltfin 4442  df-ncfin 4443  df-tfin 4444  df-evenfin 4445  df-oddfin 4446  df-sfin 4447  df-spfin 4448  df-phi 4566  df-op 4567  df-proj1 4568  df-proj2 4569  df-opab 4624  df-br 4641  df-sym 5909  df-er 5910

This theorem is referenced by:  erdmrn  5966  erth2  5970  elnc  6126