Nuprl Lemma : groupoid-square2_wf
∀G:Groupoid. ∀x00,x10,x01,x11:cat-ob(cat(G)). ∀d:cat-arrow(cat(G)) x01 x11. ∀b:cat-arrow(cat(G)) x10 x11.
∀c:cat-arrow(cat(G)) x00 x01.
  (groupoid-square2(G;x00;x10;x01;x11;b;c;d) ∈ {a:cat-arrow(cat(G)) x00 x10| a o b = c o d} )
Proof
Definitions occuring in Statement : 
groupoid-square2: groupoid-square2(G;x00;x10;x01;x11;b;c;d)
, 
groupoid-cat: cat(G)
, 
groupoid: Groupoid
, 
cat-square-commutes: x_y1 o y1_z = x_y2 o y2_z
, 
cat-arrow: cat-arrow(C)
, 
cat-ob: cat-ob(C)
, 
all: ∀x:A. B[x]
, 
member: t ∈ T
, 
set: {x:A| B[x]} 
, 
apply: f a
Definitions unfolded in proof : 
all: ∀x:A. B[x]
, 
member: t ∈ T
, 
groupoid-square2: groupoid-square2(G;x00;x10;x01;x11;b;c;d)
, 
uall: ∀[x:A]. B[x]
, 
cat-square-commutes: x_y1 o y1_z = x_y2 o y2_z
, 
prop: ℙ
, 
true: True
, 
implies: P 
⇒ Q
, 
squash: ↓T
, 
and: P ∧ Q
, 
uiff: uiff(P;Q)
, 
rev_uimplies: rev_uimplies(P;Q)
, 
uimplies: b supposing a
Lemmas referenced : 
groupoid-left-cancellation, 
cat-comp-ident, 
groupoid_inv, 
cat-comp-assoc, 
true_wf, 
squash_wf, 
uiff_transitivity3, 
cat-id_wf, 
equal_wf, 
groupoid_wf, 
cat-ob_wf, 
cat-arrow_wf, 
cat-square-commutes_wf, 
groupoid-inv_wf, 
groupoid-cat_wf, 
cat-comp_wf
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
lambdaFormation, 
cut, 
sqequalRule, 
dependent_set_memberEquality, 
applyEquality, 
lemma_by_obid, 
sqequalHypSubstitution, 
isectElimination, 
thin, 
hypothesisEquality, 
hypothesis, 
because_Cache, 
natural_numberEquality, 
independent_functionElimination, 
lambdaEquality, 
imageElimination, 
equalityTransitivity, 
equalitySymmetry, 
universeEquality, 
dependent_functionElimination, 
productElimination, 
imageMemberEquality, 
baseClosed, 
independent_isectElimination
Latex:
\mforall{}G:Groupoid.  \mforall{}x00,x10,x01,x11:cat-ob(cat(G)).  \mforall{}d:cat-arrow(cat(G))  x01  x11.
\mforall{}b:cat-arrow(cat(G))  x10  x11.  \mforall{}c:cat-arrow(cat(G))  x00  x01.
    (groupoid-square2(G;x00;x10;x01;x11;b;c;d)  \mmember{}  \{a:cat-arrow(cat(G))  x00  x10|  a  o  b  =  c  o  d\}  )
Date html generated:
2016_05_18-AM-11_56_10
Last ObjectModification:
2016_01_17-PM-02_16_54
Theory : small!categories
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