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Theorem sgnmul 30604
Description: Signum of a product. (Contributed by Thierry Arnoux, 2-Oct-2018.)
Assertion
Ref Expression
sgnmul  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  (sgn `  ( A  x.  B ) )  =  ( (sgn `  A
)  x.  (sgn `  B ) ) )

Proof of Theorem sgnmul
StepHypRef Expression
1 remulcl 10021 . . 3  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( A  x.  B
)  e.  RR )
21rexrd 10089 . 2  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( A  x.  B
)  e.  RR* )
3 eqeq1 2626 . 2  |-  ( (sgn
`  ( A  x.  B ) )  =  0  ->  ( (sgn `  ( A  x.  B
) )  =  ( (sgn `  A )  x.  (sgn `  B )
)  <->  0  =  ( (sgn `  A )  x.  (sgn `  B )
) ) )
4 eqeq1 2626 . 2  |-  ( (sgn
`  ( A  x.  B ) )  =  1  ->  ( (sgn `  ( A  x.  B
) )  =  ( (sgn `  A )  x.  (sgn `  B )
)  <->  1  =  ( (sgn `  A )  x.  (sgn `  B )
) ) )
5 eqeq1 2626 . 2  |-  ( (sgn
`  ( A  x.  B ) )  = 
-u 1  ->  (
(sgn `  ( A  x.  B ) )  =  ( (sgn `  A
)  x.  (sgn `  B ) )  <->  -u 1  =  ( (sgn `  A
)  x.  (sgn `  B ) ) ) )
6 fveq2 6191 . . . . . . 7  |-  ( A  =  0  ->  (sgn `  A )  =  (sgn
`  0 ) )
7 sgn0 13829 . . . . . . 7  |-  (sgn ` 
0 )  =  0
86, 7syl6eq 2672 . . . . . 6  |-  ( A  =  0  ->  (sgn `  A )  =  0 )
98oveq1d 6665 . . . . 5  |-  ( A  =  0  ->  (
(sgn `  A )  x.  (sgn `  B )
)  =  ( 0  x.  (sgn `  B
) ) )
109adantl 482 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  /\  A  =  0 )  ->  ( (sgn `  A )  x.  (sgn `  B ) )  =  ( 0  x.  (sgn `  B ) ) )
11 sgnclre 30601 . . . . . . 7  |-  ( B  e.  RR  ->  (sgn `  B )  e.  RR )
1211recnd 10068 . . . . . 6  |-  ( B  e.  RR  ->  (sgn `  B )  e.  CC )
1312mul02d 10234 . . . . 5  |-  ( B  e.  RR  ->  (
0  x.  (sgn `  B ) )  =  0 )
1413ad3antlr 767 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  /\  A  =  0 )  ->  ( 0  x.  (sgn `  B )
)  =  0 )
1510, 14eqtr2d 2657 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  /\  A  =  0 )  ->  0  =  ( (sgn `  A )  x.  (sgn `  B )
) )
16 fveq2 6191 . . . . . . 7  |-  ( B  =  0  ->  (sgn `  B )  =  (sgn
`  0 ) )
1716, 7syl6eq 2672 . . . . . 6  |-  ( B  =  0  ->  (sgn `  B )  =  0 )
1817oveq2d 6666 . . . . 5  |-  ( B  =  0  ->  (
(sgn `  A )  x.  (sgn `  B )
)  =  ( (sgn
`  A )  x.  0 ) )
1918adantl 482 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  /\  B  =  0 )  ->  ( (sgn `  A )  x.  (sgn `  B ) )  =  ( (sgn `  A
)  x.  0 ) )
20 sgnclre 30601 . . . . . . 7  |-  ( A  e.  RR  ->  (sgn `  A )  e.  RR )
2120recnd 10068 . . . . . 6  |-  ( A  e.  RR  ->  (sgn `  A )  e.  CC )
2221mul01d 10235 . . . . 5  |-  ( A  e.  RR  ->  (
(sgn `  A )  x.  0 )  =  0 )
2322ad3antrrr 766 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  /\  B  =  0 )  ->  ( (sgn `  A )  x.  0 )  =  0 )
2419, 23eqtr2d 2657 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  /\  B  =  0 )  ->  0  =  ( (sgn `  A )  x.  (sgn `  B )
) )
25 simpl 473 . . . . . 6  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  A  e.  RR )
2625recnd 10068 . . . . 5  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  A  e.  CC )
27 simpr 477 . . . . . 6  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  B  e.  RR )
2827recnd 10068 . . . . 5  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  B  e.  CC )
2926, 28mul0ord 10677 . . . 4  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( ( A  x.  B )  =  0  <-> 
( A  =  0  \/  B  =  0 ) ) )
3029biimpa 501 . . 3  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  ->  ( A  =  0  \/  B  =  0 ) )
3115, 24, 30mpjaodan 827 . 2  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  =  0 )  ->  0  =  ( (sgn `  A )  x.  (sgn `  B )
) )
32 simpll 790 . . . 4  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  A  e.  RR )
3332rexrd 10089 . . 3  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  A  e.  RR* )
34 oveq1 6657 . . . 4  |-  ( (sgn
`  A )  =  0  ->  ( (sgn `  A )  x.  (sgn `  B ) )  =  ( 0  x.  (sgn `  B ) ) )
3534eqeq2d 2632 . . 3  |-  ( (sgn
`  A )  =  0  ->  ( 1  =  ( (sgn `  A )  x.  (sgn `  B ) )  <->  1  =  ( 0  x.  (sgn `  B ) ) ) )
36 oveq1 6657 . . . 4  |-  ( (sgn
`  A )  =  1  ->  ( (sgn `  A )  x.  (sgn `  B ) )  =  ( 1  x.  (sgn `  B ) ) )
3736eqeq2d 2632 . . 3  |-  ( (sgn
`  A )  =  1  ->  ( 1  =  ( (sgn `  A )  x.  (sgn `  B ) )  <->  1  =  ( 1  x.  (sgn `  B ) ) ) )
38 oveq1 6657 . . . 4  |-  ( (sgn
`  A )  = 
-u 1  ->  (
(sgn `  A )  x.  (sgn `  B )
)  =  ( -u
1  x.  (sgn `  B ) ) )
3938eqeq2d 2632 . . 3  |-  ( (sgn
`  A )  = 
-u 1  ->  (
1  =  ( (sgn
`  A )  x.  (sgn `  B )
)  <->  1  =  (
-u 1  x.  (sgn `  B ) ) ) )
40 simpr 477 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  =  0 )  ->  A  =  0 )
4126adantr 481 . . . . . . 7  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  A  e.  CC )
4228adantr 481 . . . . . . 7  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  B  e.  CC )
43 simpr 477 . . . . . . . 8  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  0  <  ( A  x.  B ) )
4443gt0ne0d 10592 . . . . . . 7  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  ( A  x.  B )  =/=  0
)
4541, 42, 44mulne0bad 10682 . . . . . 6  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  A  =/=  0 )
4645neneqd 2799 . . . . 5  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  -.  A  =  0 )
4746adantr 481 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  =  0 )  ->  -.  A  =  0
)
4840, 47pm2.21dd 186 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  =  0 )  -> 
1  =  ( 0  x.  (sgn `  B
) ) )
4927ad2antrr 762 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  B  e.  RR )
5049rexrd 10089 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  B  e.  RR* )
51 simpll 790 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  ( A  e.  RR  /\  B  e.  RR ) )
52 0red 10041 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  0  e.  RR )
53 simplll 798 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  A  e.  RR )
54 simpr 477 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  0  <  A )
5552, 53, 54ltled 10185 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  0  <_  A )
56 simplr 792 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  0  <  ( A  x.  B
) )
57 prodgt0 10868 . . . . . . 7  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( 0  <_  A  /\  0  <  ( A  x.  B )
) )  ->  0  <  B )
5851, 55, 56, 57syl12anc 1324 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  0  <  B )
59 sgnp 13830 . . . . . 6  |-  ( ( B  e.  RR*  /\  0  <  B )  ->  (sgn `  B )  =  1 )
6050, 58, 59syl2anc 693 . . . . 5  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  (sgn `  B )  =  1 )
6160oveq2d 6666 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  (
1  x.  (sgn `  B ) )  =  ( 1  x.  1 ) )
62 1t1e1 11175 . . . 4  |-  ( 1  x.  1 )  =  1
6361, 62syl6req 2673 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  0  <  A )  ->  1  =  ( 1  x.  (sgn `  B )
) )
6427ad2antrr 762 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  B  e.  RR )
6564rexrd 10089 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  B  e.  RR* )
66 simplll 798 . . . . . . . . 9  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  A  e.  RR )
6766renegcld 10457 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  -u A  e.  RR )
6864renegcld 10457 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  -u B  e.  RR )
69 0red 10041 . . . . . . . . 9  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  0  e.  RR )
70 simpr 477 . . . . . . . . . 10  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  A  <  0 )
7125lt0neg1d 10597 . . . . . . . . . . 11  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( A  <  0  <->  0  <  -u A ) )
7271ad2antrr 762 . . . . . . . . . 10  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  ( A  <  0  <->  0  <  -u A ) )
7370, 72mpbid 222 . . . . . . . . 9  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  0  <  -u A )
7469, 67, 73ltled 10185 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  0  <_ 
-u A )
75 simplr 792 . . . . . . . . 9  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  0  <  ( A  x.  B
) )
7626ad2antrr 762 . . . . . . . . . 10  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  A  e.  CC )
7728ad2antrr 762 . . . . . . . . . 10  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  B  e.  CC )
7876, 77mul2negd 10485 . . . . . . . . 9  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  ( -u A  x.  -u B
)  =  ( A  x.  B ) )
7975, 78breqtrrd 4681 . . . . . . . 8  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  0  <  ( -u A  x.  -u B ) )
80 prodgt0 10868 . . . . . . . 8  |-  ( ( ( -u A  e.  RR  /\  -u B  e.  RR )  /\  (
0  <_  -u A  /\  0  <  ( -u A  x.  -u B ) ) )  ->  0  <  -u B )
8167, 68, 74, 79, 80syl22anc 1327 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  0  <  -u B )
8227lt0neg1d 10597 . . . . . . . 8  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( B  <  0  <->  0  <  -u B ) )
8382ad2antrr 762 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  ( B  <  0  <->  0  <  -u B ) )
8481, 83mpbird 247 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  B  <  0 )
85 sgnn 13834 . . . . . 6  |-  ( ( B  e.  RR*  /\  B  <  0 )  ->  (sgn `  B )  =  -u
1 )
8665, 84, 85syl2anc 693 . . . . 5  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  (sgn `  B )  =  -u
1 )
8786oveq2d 6666 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  ( -u 1  x.  (sgn `  B ) )  =  ( -u 1  x.  -u 1 ) )
88 neg1mulneg1e1 11245 . . . 4  |-  ( -u
1  x.  -u 1
)  =  1
8987, 88syl6req 2673 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B
) )  /\  A  <  0 )  ->  1  =  ( -u 1  x.  (sgn `  B )
) )
9033, 35, 37, 39, 48, 63, 89sgn3da 30603 . 2  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  0  <  ( A  x.  B )
)  ->  1  =  ( (sgn `  A )  x.  (sgn `  B )
) )
91 simpll 790 . . . 4  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0
)  ->  A  e.  RR )
9291rexrd 10089 . . 3  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0
)  ->  A  e.  RR* )
9334eqeq2d 2632 . . 3  |-  ( (sgn
`  A )  =  0  ->  ( -u 1  =  ( (sgn `  A )  x.  (sgn `  B ) )  <->  -u 1  =  ( 0  x.  (sgn `  B ) ) ) )
9436eqeq2d 2632 . . 3  |-  ( (sgn
`  A )  =  1  ->  ( -u 1  =  ( (sgn `  A )  x.  (sgn `  B ) )  <->  -u 1  =  ( 1  x.  (sgn `  B ) ) ) )
9538eqeq2d 2632 . . 3  |-  ( (sgn
`  A )  = 
-u 1  ->  ( -u 1  =  ( (sgn
`  A )  x.  (sgn `  B )
)  <->  -u 1  =  (
-u 1  x.  (sgn `  B ) ) ) )
96 simpr 477 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  ->  A  =  0 )
9726ad2antrr 762 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  ->  A  e.  CC )
9828ad2antrr 762 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  ->  B  e.  CC )
99 simplr 792 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  -> 
( A  x.  B
)  <  0 )
10099lt0ne0d 10593 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  -> 
( A  x.  B
)  =/=  0 )
10197, 98, 100mulne0bad 10682 . . . . 5  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  ->  A  =/=  0 )
102101neneqd 2799 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  ->  -.  A  =  0
)
10396, 102pm2.21dd 186 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  =  0 )  ->  -u 1  =  ( 0  x.  (sgn `  B
) ) )
10427ad2antrr 762 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  0  <  A )  ->  B  e.  RR )
105104rexrd 10089 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  0  <  A )  ->  B  e.  RR* )
106 simplr 792 . . . . . . 7  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0
)  ->  B  e.  RR )
10726, 28mulcomd 10061 . . . . . . . . 9  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( A  x.  B
)  =  ( B  x.  A ) )
108107breq1d 4663 . . . . . . . 8  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( ( A  x.  B )  <  0  <->  ( B  x.  A )  <  0 ) )
109108biimpa 501 . . . . . . 7  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0
)  ->  ( B  x.  A )  <  0
)
110106, 91, 109mul2lt0rgt0 11933 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  0  <  A )  ->  B  <  0 )
111105, 110, 85syl2anc 693 . . . . 5  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  0  <  A )  ->  (sgn `  B )  =  -u
1 )
112111oveq2d 6666 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  0  <  A )  ->  (
1  x.  (sgn `  B ) )  =  ( 1  x.  -u 1
) )
113 neg1cn 11124 . . . . 5  |-  -u 1  e.  CC
114113mulid2i 10043 . . . 4  |-  ( 1  x.  -u 1 )  = 
-u 1
115112, 114syl6req 2673 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  0  <  A )  ->  -u 1  =  ( 1  x.  (sgn `  B )
) )
116106adantr 481 . . . . . . 7  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  <  0 )  ->  B  e.  RR )
117116rexrd 10089 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  <  0 )  ->  B  e.  RR* )
118106, 91, 109mul2lt0rlt0 11932 . . . . . 6  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  <  0 )  ->  0  <  B )
119117, 118, 59syl2anc 693 . . . . 5  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  <  0 )  ->  (sgn `  B )  =  1 )
120119oveq2d 6666 . . . 4  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  <  0 )  ->  ( -u 1  x.  (sgn `  B ) )  =  ( -u 1  x.  1 ) )
121113mulid1i 10042 . . . 4  |-  ( -u
1  x.  1 )  =  -u 1
122120, 121syl6req 2673 . . 3  |-  ( ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0 )  /\  A  <  0 )  ->  -u 1  =  ( -u 1  x.  (sgn `  B )
) )
12392, 93, 94, 95, 103, 115, 122sgn3da 30603 . 2  |-  ( ( ( A  e.  RR  /\  B  e.  RR )  /\  ( A  x.  B )  <  0
)  ->  -u 1  =  ( (sgn `  A
)  x.  (sgn `  B ) ) )
1242, 3, 4, 5, 31, 90, 123sgn3da 30603 1  |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  (sgn `  ( A  x.  B ) )  =  ( (sgn `  A
)  x.  (sgn `  B ) ) )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 196    \/ wo 383    /\ wa 384    = wceq 1483    e. wcel 1990   class class class wbr 4653   ` cfv 5888  (class class class)co 6650   CCcc 9934   RRcr 9935   0cc0 9936   1c1 9937    x. cmul 9941   RR*cxr 10073    < clt 10074    <_ cle 10075   -ucneg 10267  sgncsgn 13826
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-8 1992  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602  ax-sep 4781  ax-nul 4789  ax-pow 4843  ax-pr 4906  ax-un 6949  ax-cnex 9992  ax-resscn 9993  ax-1cn 9994  ax-icn 9995  ax-addcl 9996  ax-addrcl 9997  ax-mulcl 9998  ax-mulrcl 9999  ax-mulcom 10000  ax-addass 10001  ax-mulass 10002  ax-distr 10003  ax-i2m1 10004  ax-1ne0 10005  ax-1rid 10006  ax-rnegex 10007  ax-rrecex 10008  ax-cnre 10009  ax-pre-lttri 10010  ax-pre-lttrn 10011  ax-pre-ltadd 10012  ax-pre-mulgt0 10013
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3or 1038  df-3an 1039  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-eu 2474  df-mo 2475  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ne 2795  df-nel 2898  df-ral 2917  df-rex 2918  df-reu 2919  df-rmo 2920  df-rab 2921  df-v 3202  df-sbc 3436  df-csb 3534  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-nul 3916  df-if 4087  df-pw 4160  df-sn 4178  df-pr 4180  df-tp 4182  df-op 4184  df-uni 4437  df-br 4654  df-opab 4713  df-mpt 4730  df-id 5024  df-po 5035  df-so 5036  df-xp 5120  df-rel 5121  df-cnv 5122  df-co 5123  df-dm 5124  df-rn 5125  df-res 5126  df-ima 5127  df-iota 5851  df-fun 5890  df-fn 5891  df-f 5892  df-f1 5893  df-fo 5894  df-f1o 5895  df-fv 5896  df-riota 6611  df-ov 6653  df-oprab 6654  df-mpt2 6655  df-er 7742  df-en 7956  df-dom 7957  df-sdom 7958  df-pnf 10076  df-mnf 10077  df-xr 10078  df-ltxr 10079  df-le 10080  df-sub 10268  df-neg 10269  df-div 10685  df-rp 11833  df-sgn 13827
This theorem is referenced by:  sgnmulrp2  30605  sgnmulsgn  30611  sgnmulsgp  30612
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