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Mathlib.Algebra.Field.Basic

Lemmas about division (semi)rings and (semi)fields #

theorem add_div {α : Type u_1} [DivisionSemiring α] (a : α) (b : α) (c : α) :
(a + b) / c = a / c + b / c
theorem div_add_div_same {α : Type u_1} [DivisionSemiring α] (a : α) (b : α) (c : α) :
a / c + b / c = (a + b) / c
theorem same_add_div {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (h : b 0) :
(b + a) / b = 1 + a / b
theorem div_add_same {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (h : b 0) :
(a + b) / b = a / b + 1
theorem one_add_div {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (h : b 0) :
1 + a / b = (b + a) / b
theorem div_add_one {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (h : b 0) :
a / b + 1 = (a + b) / b
theorem one_div_mul_add_mul_one_div_eq_one_div_add_one_div {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (ha : a 0) (hb : b 0) :
1 / a * (a + b) * (1 / b) = 1 / a + 1 / b
theorem add_div_eq_mul_add_div {α : Type u_1} [DivisionSemiring α] {c : α} (a : α) (b : α) (hc : c 0) :
a + b / c = (a * c + b) / c
theorem add_div' {α : Type u_1} [DivisionSemiring α] (a : α) (b : α) (c : α) (hc : c 0) :
b + a / c = (b * c + a) / c
theorem div_add' {α : Type u_1} [DivisionSemiring α] (a : α) (b : α) (c : α) (hc : c 0) :
a / c + b = (a + b * c) / c
theorem Commute.div_add_div {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} {c : α} {d : α} (hbc : Commute b c) (hbd : Commute b d) (hb : b 0) (hd : d 0) :
a / b + c / d = (a * d + b * c) / (b * d)
theorem Commute.one_div_add_one_div {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (hab : Commute a b) (ha : a 0) (hb : b 0) :
1 / a + 1 / b = (a + b) / (a * b)
theorem Commute.inv_add_inv {α : Type u_1} [DivisionSemiring α] {a : α} {b : α} (hab : Commute a b) (ha : a 0) (hb : b 0) :
a⁻¹ + b⁻¹ = (a + b) / (a * b)
theorem one_div_neg_eq_neg_one_div {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] (a : K) :
1 / -a = -(1 / a)
theorem div_neg_eq_neg_div {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] (a : K) (b : K) :
b / -a = -(b / a)
theorem neg_div {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] (a : K) (b : K) :
-b / a = -(b / a)
theorem neg_div' {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] (a : K) (b : K) :
-(b / a) = -b / a
theorem neg_div_neg_eq {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] (a : K) (b : K) :
-a / -b = a / b
theorem neg_inv {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] {a : K} :
theorem div_neg {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] {b : K} (a : K) :
a / -b = -(a / b)
theorem inv_neg {K : Type u_3} [DivisionMonoid K] [HasDistribNeg K] {a : K} :
@[simp]
theorem div_neg_self {K : Type u_3} [DivisionRing K] {a : K} (h : a 0) :
a / -a = -1
@[simp]
theorem neg_div_self {K : Type u_3} [DivisionRing K] {a : K} (h : a 0) :
-a / a = -1
theorem div_sub_div_same {K : Type u_3} [DivisionRing K] (a : K) (b : K) (c : K) :
a / c - b / c = (a - b) / c
theorem same_sub_div {K : Type u_3} [DivisionRing K] {a : K} {b : K} (h : b 0) :
(b - a) / b = 1 - a / b
theorem one_sub_div {K : Type u_3} [DivisionRing K] {a : K} {b : K} (h : b 0) :
1 - a / b = (b - a) / b
theorem div_sub_same {K : Type u_3} [DivisionRing K] {a : K} {b : K} (h : b 0) :
(a - b) / b = a / b - 1
theorem div_sub_one {K : Type u_3} [DivisionRing K] {a : K} {b : K} (h : b 0) :
a / b - 1 = (a - b) / b
theorem sub_div {K : Type u_3} [DivisionRing K] (a : K) (b : K) (c : K) :
(a - b) / c = a / c - b / c
theorem inv_sub_inv' {K : Type u_3} [DivisionRing K] {a : K} {b : K} (ha : a 0) (hb : b 0) :
a⁻¹ - b⁻¹ = a⁻¹ * (b - a) * b⁻¹

See inv_sub_inv for the more convenient version when K is commutative.

theorem one_div_mul_sub_mul_one_div_eq_one_div_add_one_div {K : Type u_3} [DivisionRing K] {a : K} {b : K} (ha : a 0) (hb : b 0) :
1 / a * (b - a) * (1 / b) = 1 / a - 1 / b
theorem Commute.div_sub_div {K : Type u_3} [DivisionRing K] {a : K} {b : K} {c : K} {d : K} (hbc : Commute b c) (hbd : Commute b d) (hb : b 0) (hd : d 0) :
a / b - c / d = (a * d - b * c) / (b * d)
theorem Commute.inv_sub_inv {K : Type u_3} [DivisionRing K] {a : K} {b : K} (hab : Commute a b) (ha : a 0) (hb : b 0) :
a⁻¹ - b⁻¹ = (b - a) / (a * b)
theorem div_add_div {α : Type u_1} [Semifield α] {b : α} {d : α} (a : α) (c : α) (hb : b 0) (hd : d 0) :
a / b + c / d = (a * d + b * c) / (b * d)
theorem one_div_add_one_div {α : Type u_1} [Semifield α] {a : α} {b : α} (ha : a 0) (hb : b 0) :
1 / a + 1 / b = (a + b) / (a * b)
theorem inv_add_inv {α : Type u_1} [Semifield α] {a : α} {b : α} (ha : a 0) (hb : b 0) :
a⁻¹ + b⁻¹ = (a + b) / (a * b)
theorem div_sub_div {K : Type u_3} [Field K] (a : K) {b : K} (c : K) {d : K} (hb : b 0) (hd : d 0) :
a / b - c / d = (a * d - b * c) / (b * d)
theorem inv_sub_inv {K : Type u_3} [Field K] {a : K} {b : K} (ha : a 0) (hb : b 0) :
a⁻¹ - b⁻¹ = (b - a) / (a * b)
theorem sub_div' {K : Type u_3} [Field K] (a : K) (b : K) (c : K) (hc : c 0) :
b - a / c = (b * c - a) / c
theorem div_sub' {K : Type u_3} [Field K] (a : K) (b : K) (c : K) (hc : c 0) :
a / c - b = (a - c * b) / c
theorem RingHom.injective {α : Type u_1} {β : Type u_2} [DivisionRing α] [Semiring β] [Nontrivial β] (f : α →+* β) :
noncomputable def divisionRingOfIsUnitOrEqZero {R : Type u_4} [Nontrivial R] [hR : Ring R] (h : ∀ (a : R), IsUnit a a = 0) :

Constructs a DivisionRing structure on a Ring consisting only of units and 0.

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Instances For
    @[reducible]
    noncomputable def fieldOfIsUnitOrEqZero {R : Type u_4} [Nontrivial R] [hR : CommRing R] (h : ∀ (a : R), IsUnit a a = 0) :

    Constructs a Field structure on a CommRing consisting only of units and 0. See note [reducible non-instances].

    Equations
    Instances For
      @[reducible]
      def Function.Injective.divisionSemiring {α : Type u_1} {β : Type u_2} [DivisionSemiring β] [Zero α] [Mul α] [Add α] [One α] [Inv α] [Div α] [SMul α] [Pow α ] [Pow α ] [NatCast α] (f : αβ) (hf : Function.Injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : α), f (x + y) = f x + f y) (mul : ∀ (x y : α), f (x * y) = f x * f y) (inv : ∀ (x : α), f x⁻¹ = (f x)⁻¹) (div : ∀ (x y : α), f (x / y) = f x / f y) (nsmul : ∀ (x : α) (n : ), f (n x) = n f x) (npow : ∀ (x : α) (n : ), f (x ^ n) = f x ^ n) (zpow : ∀ (x : α) (n : ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ), f n = n) :

      Pullback a DivisionSemiring along an injective function.

      Equations
      • One or more equations did not get rendered due to their size.
      Instances For
        @[reducible]
        def Function.Injective.divisionRing {K : Type u_3} [DivisionRing K] {K' : Type u_4} [Zero K'] [One K'] [Add K'] [Mul K'] [Neg K'] [Sub K'] [Inv K'] [Div K'] [SMul K'] [SMul K'] [SMul K'] [Pow K' ] [Pow K' ] [NatCast K'] [IntCast K'] [RatCast K'] (f : K'K) (hf : Function.Injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : K'), f (x + y) = f x + f y) (mul : ∀ (x y : K'), f (x * y) = f x * f y) (neg : ∀ (x : K'), f (-x) = -f x) (sub : ∀ (x y : K'), f (x - y) = f x - f y) (inv : ∀ (x : K'), f x⁻¹ = (f x)⁻¹) (div : ∀ (x y : K'), f (x / y) = f x / f y) (nsmul : ∀ (x : K') (n : ), f (n x) = n f x) (zsmul : ∀ (x : K') (n : ), f (n x) = n f x) (qsmul : ∀ (x : K') (n : ), f (n x) = n f x) (npow : ∀ (x : K') (n : ), f (x ^ n) = f x ^ n) (zpow : ∀ (x : K') (n : ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ), f n = n) (int_cast : ∀ (n : ), f n = n) (rat_cast : ∀ (n : ), f n = n) :

        Pullback a DivisionSemiring along an injective function. See note [reducible non-instances].

        Equations
        • One or more equations did not get rendered due to their size.
        Instances For
          @[reducible]
          def Function.Injective.semifield {α : Type u_1} {β : Type u_2} [Semifield β] [Zero α] [Mul α] [Add α] [One α] [Inv α] [Div α] [SMul α] [Pow α ] [Pow α ] [NatCast α] (f : αβ) (hf : Function.Injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : α), f (x + y) = f x + f y) (mul : ∀ (x y : α), f (x * y) = f x * f y) (inv : ∀ (x : α), f x⁻¹ = (f x)⁻¹) (div : ∀ (x y : α), f (x / y) = f x / f y) (nsmul : ∀ (x : α) (n : ), f (n x) = n f x) (npow : ∀ (x : α) (n : ), f (x ^ n) = f x ^ n) (zpow : ∀ (x : α) (n : ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ), f n = n) :

          Pullback a Field along an injective function.

          Equations
          • One or more equations did not get rendered due to their size.
          Instances For
            @[reducible]
            def Function.Injective.field {K : Type u_3} [Field K] {K' : Type u_4} [Zero K'] [Mul K'] [Add K'] [Neg K'] [Sub K'] [One K'] [Inv K'] [Div K'] [SMul K'] [SMul K'] [SMul K'] [Pow K' ] [Pow K' ] [NatCast K'] [IntCast K'] [RatCast K'] (f : K'K) (hf : Function.Injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : K'), f (x + y) = f x + f y) (mul : ∀ (x y : K'), f (x * y) = f x * f y) (neg : ∀ (x : K'), f (-x) = -f x) (sub : ∀ (x y : K'), f (x - y) = f x - f y) (inv : ∀ (x : K'), f x⁻¹ = (f x)⁻¹) (div : ∀ (x y : K'), f (x / y) = f x / f y) (nsmul : ∀ (x : K') (n : ), f (n x) = n f x) (zsmul : ∀ (x : K') (n : ), f (n x) = n f x) (qsmul : ∀ (x : K') (n : ), f (n x) = n f x) (npow : ∀ (x : K') (n : ), f (x ^ n) = f x ^ n) (zpow : ∀ (x : K') (n : ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ), f n = n) (int_cast : ∀ (n : ), f n = n) (rat_cast : ∀ (n : ), f n = n) :

            Pullback a Field along an injective function. See note [reducible non-instances].

            Equations
            • One or more equations did not get rendered due to their size.
            Instances For

              Order dual #

              instance instRatCastOrderDual {α : Type u_1} [h : RatCast α] :
              Equations
              • instRatCastOrderDual = h
              Equations
              • instDivisionSemiringOrderDual = h
              Equations
              • instDivisionRingOrderDual = h
              instance instSemifieldOrderDual {α : Type u_1} [h : Semifield α] :
              Equations
              • instSemifieldOrderDual = h
              instance instFieldOrderDual {α : Type u_1} [h : Field α] :
              Equations
              • instFieldOrderDual = h
              @[simp]
              theorem toDual_rat_cast {α : Type u_1} [RatCast α] (n : ) :
              OrderDual.toDual n = n
              @[simp]
              theorem ofDual_rat_cast {α : Type u_1} [RatCast α] (n : ) :
              ↑(OrderDual.ofDual n) = n

              Lexicographic order #

              instance instRatCastLex {α : Type u_1} [h : RatCast α] :
              Equations
              • instRatCastLex = h
              Equations
              • instDivisionSemiringLex = h
              instance instDivisionRingLex {α : Type u_1} [h : DivisionRing α] :
              Equations
              • instDivisionRingLex = h
              instance instSemifieldLex {α : Type u_1} [h : Semifield α] :
              Equations
              • instSemifieldLex = h
              instance instFieldLex {α : Type u_1} [h : Field α] :
              Field (Lex α)
              Equations
              • instFieldLex = h
              @[simp]
              theorem toLex_rat_cast {α : Type u_1} [RatCast α] (n : ) :
              toLex n = n
              @[simp]
              theorem ofLex_rat_cast {α : Type u_1} [RatCast α] (n : ) :
              ↑(ofLex n) = n