Theorem xnegeq 9829

Description: Equality of two extended numbers with -e in front of them. (Contributed by FL, 26-Dec-2011.) (Proof shortened by Mario Carneiro, 20-Aug-2015.)

Assertion

Ref	Expression
xnegeq	|- ( A = B -> -e A = -e B )

Proof of Theorem xnegeq

Step	Hyp	Ref	Expression
1		eqeq1 2184	. . 3 |- ( A = B -> ( A = +oo <-> B = +oo ) )
2		eqeq1 2184	. . . 4 |- ( A = B -> ( A = -oo <-> B = -oo ) )
3		negeq 8152	. . . 4 |- ( A = B -> -u A = -u B )
4	2, 3	ifbieq2d 3560	. . 3 |- ( A = B -> if ( A = -oo , +oo , -u A ) = if ( B = -oo , +oo , -u B ) )
5	1, 4	ifbieq2d 3560	. 2 |- ( A = B -> if ( A = +oo , -oo , if ( A = -oo , +oo , -u A ) ) = if ( B = +oo , -oo , if ( B = -oo , +oo , -u B ) ) )
6		df-xneg 9774	. 2 |- -e A = if ( A = +oo , -oo , if ( A = -oo , +oo , -u A ) )
7		df-xneg 9774	. 2 |- -e B = if ( B = +oo , -oo , if ( B = -oo , +oo , -u B ) )
8	5, 6, 7	3eqtr4g 2235	1 |- ( A = B -> -e A = -e B )

Syntax hints:   -> wi 4   = wceq 1353   ifcif 3536   +oocpnf 7991   -oocmnf 7992   -ucneg 8131   -ecxne 9771

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 614  ax-in2 615  ax-io 709  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-10 1505  ax-11 1506  ax-i12 1507  ax-bndl 1509  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-ext 2159

This theorem depends on definitions:  df-bi 117  df-3an 980  df-tru 1356  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-nfc 2308  df-rex 2461  df-rab 2464  df-v 2741  df-un 3135  df-if 3537  df-sn 3600  df-pr 3601  df-op 3603  df-uni 3812  df-br 4006  df-iota 5180  df-fv 5226  df-ov 5880  df-neg 8133  df-xneg 9774

This theorem is referenced by:  xnegcl  9834  xnegneg  9835  xneg11  9836  xltnegi  9837  xnegid  9861  xnegdi  9870  xsubge0  9883  xposdif  9884  xlesubadd  9885  xrnegiso  11272  infxrnegsupex  11273  xrminmax  11275  xrminrecl  11283  xrminadd  11285  xblss2ps  13943  xblss2  13944