Definition df-trkg

Description: Define the class of Tarski geometries. A Tarski geometry is a set of points, equipped with a betweenness relation (denoting that a point lies on a line segment between two other points) and a congruence relation (denoting equality of line segment lengths).

Here, we are using the following:

Tarski originally had more axioms, but later reduced his list to 11:

Our definition is split into 5 parts:

So our definition of a Tarskian Geometry includes the 3 axioms for the quaternary congruence relation (A1, A2, A3), the 3 axioms for the ternary betweenness relation (A6, A7, A11), and the 2 axioms of compatibility of the congruence and the betweenness relations (A4,A5).

It does not include Euclid's axiom A10, nor the 2-dimensional axioms A8 (Lower dimension axiom) and A9 (Upper dimension axiom) so the number of dimensions of the geometry it formalizes is not constrained.

Considering A2 as one of the 3 axioms for the quaternary congruence relation is somewhat conventional, because the transitivity of the congruence relation is automatically given by our choice to take the distance as this congruence relation in our definition of Tarski geometries. (Contributed by Thierry Arnoux, 24-Aug-2017) (Revised by Thierry Arnoux, 27-Apr-2019)

	Ref	Expression
Assertion	df-trkg	$$⊢{𝒢}_{\mathrm{Tarski}}=\left({𝒢}_{\mathrm{Tarski}}^C\cap {𝒢}_{\mathrm{Tarski}}^B\right)\cap \left({𝒢}_{\mathrm{Tarski}}^{\mathrm{CB}}\cap \left\{f|\underset{\dot{}}{[}{\mathrm{Base}}_f/p\underset{\dot{}}{]}\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)\right\}\right)$$

Detailed syntax breakdown

Step	Hyp	Ref	Expression
0		cstrkg	$$class{𝒢}_{\mathrm{Tarski}}$$
1		cstrkgc	$$class{𝒢}_{\mathrm{Tarski}}^C$$
2		cstrkgb	$$class{𝒢}_{\mathrm{Tarski}}^B$$
3	1 2	cin	$$class\left({𝒢}_{\mathrm{Tarski}}^C\cap {𝒢}_{\mathrm{Tarski}}^B\right)$$
4		cstrkgcb	$$class{𝒢}_{\mathrm{Tarski}}^{\mathrm{CB}}$$
5		vf	$$setvarf$$
6		cbs	$$class\mathrm{Base}$$
7	5	cv	$$setvarf$$
8	7 6	cfv	$$class{\mathrm{Base}}_f$$
9		vp	$$setvarp$$
10		citv	$$class\mathrm{Itv}$$
11	7 10	cfv	$$class\mathrm{Itv}\left(f\right)$$
12		vi	$$setvari$$
13		clng	$$class{Line}_{𝒢}$$
14	7 13	cfv	$$class{Line}_{𝒢}\left(f\right)$$
15		vx	$$setvarx$$
16	9	cv	$$setvarp$$
17		vy	$$setvary$$
18	15	cv	$$setvarx$$
19	18	csn	$$class\left\{x\right\}$$
20	16 19	cdif	$$class\left(p\setminus \left\{x\right\}\right)$$
21		vz	$$setvarz$$
22	21	cv	$$setvarz$$
23	12	cv	$$setvari$$
24	17	cv	$$setvary$$
25	18 24 23	co	$$class\left(xiy\right)$$
26	22 25	wcel	$$wffz\in \left(xiy\right)$$
27	22 24 23	co	$$class\left(ziy\right)$$
28	18 27	wcel	$$wffx\in \left(ziy\right)$$
29	18 22 23	co	$$class\left(xiz\right)$$
30	24 29	wcel	$$wffy\in \left(xiz\right)$$
31	26 28 30	w3o	$$wff\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)$$
32	31 21 16	crab	$$class\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}$$
33	15 17 16 20 32	cmpo	$$class\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)$$
34	14 33	wceq	$$wff{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)$$
35	34 12 11	wsbc	$$wff\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)$$
36	35 9 8	wsbc	$$wff\underset{\dot{}}{[}{\mathrm{Base}}_f/p\underset{\dot{}}{]}\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)$$
37	36 5	cab	$$class\left\{f|\underset{\dot{}}{[}{\mathrm{Base}}_f/p\underset{\dot{}}{]}\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)\right\}$$
38	4 37	cin	$$class\left({𝒢}_{\mathrm{Tarski}}^{\mathrm{CB}}\cap \left\{f|\underset{\dot{}}{[}{\mathrm{Base}}_f/p\underset{\dot{}}{]}\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)\right\}\right)$$
39	3 38	cin	$$class\left(\left({𝒢}_{\mathrm{Tarski}}^C\cap {𝒢}_{\mathrm{Tarski}}^B\right)\cap \left({𝒢}_{\mathrm{Tarski}}^{\mathrm{CB}}\cap \left\{f|\underset{\dot{}}{[}{\mathrm{Base}}_f/p\underset{\dot{}}{]}\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)\right\}\right)\right)$$
40	0 39	wceq	$$wff{𝒢}_{\mathrm{Tarski}}=\left({𝒢}_{\mathrm{Tarski}}^C\cap {𝒢}_{\mathrm{Tarski}}^B\right)\cap \left({𝒢}_{\mathrm{Tarski}}^{\mathrm{CB}}\cap \left\{f|\underset{\dot{}}{[}{\mathrm{Base}}_f/p\underset{\dot{}}{]}\underset{\dot{}}{[}\mathrm{Itv}\left(f\right)/i\underset{\dot{}}{]}{Line}_{𝒢}\left(f\right)=\left(x\in p,y\in \left(p\setminus \left\{x\right\}\right)⟼\left\{z\in p|\left(z\in \left(xiy\right)\vee x\in \left(ziy\right)\vee y\in \left(xiz\right)\right)\right\}\right)\right\}\right)$$