Nuprl - Some Definitions

biject	`Def Bij(A; B; f) == Inj(A; B; f) & Surj(A; B; f)` `Thm* A,B:Type, f:(AB). Bij(A; B; f) Prop`
equiv_rel	`Def EquivRel x,y:T. E(x;y) == Refl(T;x,y.E(x;y)) & Sym x,y:T. E(x;y) & Trans x,y:T. E(x;y)` `Thm* T:Type, E:(TTProp). (EquivRel x,y:T. E(x,y)) Prop`
preima_of_rel	`Def R_f(x,y) == (f(x)) R (f(y))` `Thm* A,B:Type, f:(AB), R:(BBProp). R_f AAProp`
surject	`Def Surj(A; B; f) == b:B. a:A. f(a) = b` `Thm* A,B:Type, f:(AB). Surj(A; B; f) Prop`
inject	`Def Inj(A; B; f) == a1,a2:A. f(a1) = f(a2) B a1 = a2` `Thm* A,B:Type, f:(AB). Inj(A; B; f) Prop`
trans	`Def Trans x,y:T. E(x;y) == a,b,c:T. E(a;b) E(b;c) E(a;c)` `Thm* T:Type, E:(TTProp). Trans x,y:T. E(x,y) Prop`
sym	`Def Sym x,y:T. E(x;y) == a,b:T. E(a;b) E(b;a)` `Thm* T:Type, E:(TTProp). Sym x,y:T. E(x,y) Prop`
refl	`Def Refl(T;x,y.E(x;y)) == a:T. E(a;a)` `Thm* T:Type, E:(TTProp). Refl(T;x,y.E(x,y)) Prop`

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