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some stuff about exact couples

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This commit is contained in:
Egbert Rijke 2017-05-11 17:25:02 -04:00
parent 922baa9975
commit eaf7290def
1 changed files with 9 additions and 1 deletions
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10
algebra/exact_couple.hlean
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@ -131,12 +131,20 @@ definition SES_of_exact_couple_at_i : SES (ab_kernel i) A (ab_image i) :=
fapply ab_group_first_iso_thm i,
end
definition kj_zero (a : A) : k (j a) = 1 :=
begin
exact sorry
end
definition j_factor : A →g (ab_kernel d) :=
begin
fapply ab_hom_lift j,
intro a,
unfold kernel_subgroup,
exact sorry --refine ap (group_fun j) _,
exact calc
d (j a) = j (k (j a)) : rfl
... = j 1 : by exact ap j (kj_zero a)
... = 1 : to_respect_one,
end