Nuprl Lemma : length-copath-extend
∀[A:𝕌']. ∀[B:A ⟶ Type]. ∀[w:coW(A;a.B[a])]. ∀[p:copath(a.B[a];w)]. ∀[t:Top].
  (copath-length(copath-extend(p;t)) = (copath-length(p) + 1) ∈ ℤ)
Proof
Definitions occuring in Statement : 
copath-length: copath-length(p), 
copath-extend: copath-extend(q;t), 
copath: copath(a.B[a];w), 
coW: coW(A;a.B[a]), 
uall: ∀[x:A]. B[x], 
top: Top, 
so_apply: x[s], 
function: x:A ⟶ B[x], 
add: n + m, 
natural_number: $n, 
int: ℤ, 
universe: Type, 
equal: s = t ∈ T
Definitions unfolded in proof : 
so_apply: x[s], 
so_lambda: λ2x.t[x], 
nat: ℕ, 
pi1: fst(t), 
copath-extend: copath-extend(q;t), 
copath-length: copath-length(p), 
copath: copath(a.B[a];w), 
member: t ∈ T, 
uall: ∀[x:A]. B[x]
Lemmas referenced : 
coW_wf, 
copath_wf, 
top_wf
Rules used in proof : 
universeEquality, 
functionEquality, 
cumulativity, 
instantiate, 
applyEquality, 
lambdaEquality, 
because_Cache, 
axiomEquality, 
isectElimination, 
isect_memberEquality, 
extract_by_obid, 
natural_numberEquality, 
hypothesis, 
hypothesisEquality, 
rename, 
setElimination, 
addEquality, 
sqequalRule, 
thin, 
productElimination, 
sqequalHypSubstitution, 
cut, 
introduction, 
isect_memberFormation, 
sqequalReflexivity, 
computationStep, 
sqequalTransitivity, 
sqequalSubstitution
Latex:
\mforall{}[A:\mBbbU{}'].  \mforall{}[B:A  {}\mrightarrow{}  Type].  \mforall{}[w:coW(A;a.B[a])].  \mforall{}[p:copath(a.B[a];w)].  \mforall{}[t:Top].
    (copath-length(copath-extend(p;t))  =  (copath-length(p)  +  1))
 Date html generated: 
2018_07_25-PM-01_40_12
 Last ObjectModification: 
2018_07_24-PM-05_40_26
Theory : co-recursion
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