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Definition df-bj-addc 33125
Description: Define the additions on the extended complex numbers (on the subset of  (CCbar  X. CCbar ) where it makes sense) and on the complex projective line (Riemann sphere). (Contributed by BJ, 22-Jun-2019.)
Assertion
Ref Expression
df-bj-addc  |- +cc  =  ( x  e.  ( ( ( CC  X. CCbar )  u.  (CCbar  X.  CC )
)  u.  ( (CChat 
X. CChat )  u.  (Diag ` CCinfty
) ) )  |->  if ( ( ( 1st `  x )  = infty  \/  ( 2nd `  x )  = infty ) , infty ,  if ( ( 1st `  x
)  e.  CC ,  if ( ( 2nd `  x
)  e.  CC , 
( ( 1st `  x
)  +  ( 2nd `  x ) ) ,  ( 2nd `  x
) ) ,  ( 1st `  x ) ) ) )

Detailed syntax breakdown of Definition df-bj-addc
StepHypRef Expression
1 caddcc 33124 . 2  class +cc
2 vx . . 3  setvar  x
3 cc 9934 . . . . . 6  class  CC
4 cccbar 33102 . . . . . 6  class CCbar
53, 4cxp 5112 . . . . 5  class  ( CC 
X. CCbar )
64, 3cxp 5112 . . . . 5  class  (CCbar  X.  CC )
75, 6cun 3572 . . . 4  class  ( ( CC  X. CCbar )  u.  (CCbar  X.  CC ) )
8 ccchat 33119 . . . . . 6  class CChat
98, 8cxp 5112 . . . . 5  class  (CChat  X. CChat )
10 cccinfty 33098 . . . . . 6  class CCinfty
11 cdiag2 33088 . . . . . 6  class Diag
1210, 11cfv 5888 . . . . 5  class  (Diag ` CCinfty )
139, 12cun 3572 . . . 4  class  ( (CChat 
X. CChat )  u.  (Diag ` CCinfty
) )
147, 13cun 3572 . . 3  class  ( ( ( CC  X. CCbar )  u.  (CCbar  X.  CC )
)  u.  ( (CChat 
X. CChat )  u.  (Diag ` CCinfty
) ) )
152cv 1482 . . . . . . 7  class  x
16 c1st 7166 . . . . . . 7  class  1st
1715, 16cfv 5888 . . . . . 6  class  ( 1st `  x )
18 cinfty 33117 . . . . . 6  class infty
1917, 18wceq 1483 . . . . 5  wff  ( 1st `  x )  = infty
20 c2nd 7167 . . . . . . 7  class  2nd
2115, 20cfv 5888 . . . . . 6  class  ( 2nd `  x )
2221, 18wceq 1483 . . . . 5  wff  ( 2nd `  x )  = infty
2319, 22wo 383 . . . 4  wff  ( ( 1st `  x )  = infty  \/  ( 2nd `  x )  = infty )
2417, 3wcel 1990 . . . . 5  wff  ( 1st `  x )  e.  CC
2521, 3wcel 1990 . . . . . 6  wff  ( 2nd `  x )  e.  CC
26 caddc 9939 . . . . . . 7  class  +
2717, 21, 26co 6650 . . . . . 6  class  ( ( 1st `  x )  +  ( 2nd `  x
) )
2825, 27, 21cif 4086 . . . . 5  class  if ( ( 2nd `  x
)  e.  CC , 
( ( 1st `  x
)  +  ( 2nd `  x ) ) ,  ( 2nd `  x
) )
2924, 28, 17cif 4086 . . . 4  class  if ( ( 1st `  x
)  e.  CC ,  if ( ( 2nd `  x
)  e.  CC , 
( ( 1st `  x
)  +  ( 2nd `  x ) ) ,  ( 2nd `  x
) ) ,  ( 1st `  x ) )
3023, 18, 29cif 4086 . . 3  class  if ( ( ( 1st `  x
)  = infty  \/  ( 2nd `  x )  = infty ) , infty ,  if ( ( 1st `  x
)  e.  CC ,  if ( ( 2nd `  x
)  e.  CC , 
( ( 1st `  x
)  +  ( 2nd `  x ) ) ,  ( 2nd `  x
) ) ,  ( 1st `  x ) ) )
312, 14, 30cmpt 4729 . 2  class  ( x  e.  ( ( ( CC  X. CCbar )  u.  (CCbar  X.  CC ) )  u.  ( (CChat  X. CChat )  u.  (Diag ` CCinfty ) ) )  |->  if ( ( ( 1st `  x
)  = infty  \/  ( 2nd `  x )  = infty ) , infty ,  if ( ( 1st `  x
)  e.  CC ,  if ( ( 2nd `  x
)  e.  CC , 
( ( 1st `  x
)  +  ( 2nd `  x ) ) ,  ( 2nd `  x
) ) ,  ( 1st `  x ) ) ) )
321, 31wceq 1483 1  wff +cc  =  ( x  e.  ( ( ( CC  X. CCbar )  u.  (CCbar  X.  CC )
)  u.  ( (CChat 
X. CChat )  u.  (Diag ` CCinfty
) ) )  |->  if ( ( ( 1st `  x )  = infty  \/  ( 2nd `  x )  = infty ) , infty ,  if ( ( 1st `  x
)  e.  CC ,  if ( ( 2nd `  x
)  e.  CC , 
( ( 1st `  x
)  +  ( 2nd `  x ) ) ,  ( 2nd `  x
) ) ,  ( 1st `  x ) ) ) )
Colors of variables: wff setvar class
This definition is referenced by: (None)
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