Definition df-plpq 6328

Description: Define pre-addition on positive fractions. This is a "temporary" set used in the construction of complex numbers, and is intended to be used only by the construction. This "pre-addition" operation works directly with ordered pairs of integers. The actual positive fraction addition +_Q (df-plqqs 6333) works with the equivalence classes of these ordered pairs determined by the equivalence relation ~_Q (df-enq 6331). (Analogous remarks apply to the other "pre-" operations in the complex number construction that follows.) From Proposition 9-2.3 of [Gleason] p. 117. (Contributed by NM, 28-Aug-1995.)

Assertion

Ref	Expression
df-plpq	⊢ +pQ = (x ∈ (N × N), y ∈ (N × N) ↦ ⟨(((1st ‘x) ·N (2nd ‘y)) +N ((1st ‘y) ·N (2nd ‘x))), ((2nd ‘x) ·N (2nd ‘y))⟩)

Distinct variable group:   x,y

Detailed syntax breakdown of Definition df-plpq

Step	Hyp	Ref	Expression
1		cplpq 6260	. 2 class +pQ
2		vx	. . 3 setvar x
3		vy	. . 3 setvar y
4		cnpi 6256	. . . 4 class N
5	4, 4	cxp 4286	. . 3 class (N × N)
6	2	cv 1241	. . . . . . 7 class x
7		c1st 5707	. . . . . . 7 class 1st
8	6, 7	cfv 4845	. . . . . 6 class (1st ‘x)
9	3	cv 1241	. . . . . . 7 class y
10		c2nd 5708	. . . . . . 7 class 2nd
11	9, 10	cfv 4845	. . . . . 6 class (2nd ‘y)
12		cmi 6258	. . . . . 6 class ·N
13	8, 11, 12	co 5455	. . . . 5 class ((1st ‘x) ·N (2nd ‘y))
14	9, 7	cfv 4845	. . . . . 6 class (1st ‘y)
15	6, 10	cfv 4845	. . . . . 6 class (2nd ‘x)
16	14, 15, 12	co 5455	. . . . 5 class ((1st ‘y) ·N (2nd ‘x))
17		cpli 6257	. . . . 5 class +N
18	13, 16, 17	co 5455	. . . 4 class (((1st ‘x) ·N (2nd ‘y)) +N ((1st ‘y) ·N (2nd ‘x)))
19	15, 11, 12	co 5455	. . . 4 class ((2nd ‘x) ·N (2nd ‘y))
20	18, 19	cop 3370	. . 3 class ⟨(((1st ‘x) ·N (2nd ‘y)) +N ((1st ‘y) ·N (2nd ‘x))), ((2nd ‘x) ·N (2nd ‘y))⟩
21	2, 3, 5, 5, 20	cmpt2 5457	. 2 class (x ∈ (N × N), y ∈ (N × N) ↦ ⟨(((1st ‘x) ·N (2nd ‘y)) +N ((1st ‘y) ·N (2nd ‘x))), ((2nd ‘x) ·N (2nd ‘y))⟩)
22	1, 21	wceq 1242	1 wff +pQ = (x ∈ (N × N), y ∈ (N × N) ↦ ⟨(((1st ‘x) ·N (2nd ‘y)) +N ((1st ‘y) ·N (2nd ‘x))), ((2nd ‘x) ·N (2nd ‘y))⟩)

This definition is referenced by:  dfplpq2  6338