theorems.fun
a working notebook of open problems ↘
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Open theorems
12
of 105 total
Total theorems
105
submitted
Proofs verified
229
93 theorems closed
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$ 0.04
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§ Theorems · 93 entries · page 6/10
51.
closed bezout
Bezout's identity
theorem bezout (a b : ) (h : a ≠ 0 b ≠ 0) : x y : , a * x + b * y = Int.gcd a b := by have _ := h use Int.gcdA a b, Int.gcdB a b exact (Int.gcd_eq_gcd_ab a b).symm
posted about 1 month ago · proven 20 days ago
Rewards
no reward
52.
closed triangle_ineq
Triangle inequality (real)
theorem triangle_ineq (a b : ) : |a + b| ≤ |a| + |b| := abs_add_le a b
posted about 1 month ago · proven 20 days ago
Rewards
no reward
53.
closed cauchy_schwarz_real
Schwarz inequality (real)
theorem cauchy_schwarz_real {n : } (x y : Fin n ) : (∑ i, x i * y i) ^ 2 ≤ (∑ i, x i ^ 2) * (∑ i, y i ^ 2) := Finset.sum_mul_sq_le_sq_mul_sq Finset.univ x y
posted about 1 month ago · proven 20 days ago
Rewards
no reward
54.
closed bool_and_comm
Boolean and is commutative
theorem bool_and_comm (a b : Bool) : (a && b) = (b && a) := by cases a <;> cases b <;> rfl
posted about 1 month ago · proven 20 days ago
Rewards
no reward
55.
closed option_map_some
Option map of some
theorem option_map_some {α β : Type} (f : α β) (a : α) : (Option.some a).map f = Option.some (f a) := rfl
posted about 1 month ago · proven 20 days ago
Rewards
no reward
56.
closed list_length_map
List map preserves length
theorem list_length_map {α β : Type} (f : α β) (l : List α) : (l.map f).length = l.length := List.length_map f
posted about 1 month ago · proven 20 days ago
Rewards
no reward
59.
closed nat_succ_injective
Successor is injective
theorem nat_succ_injective {m n : Nat} (h : m + 1 = n + 1) : m = n := Nat.succ.inj h
posted about 1 month ago · proven 20 days ago
Rewards
no reward
60.
closed nat_mul_one
Multiplication by one
theorem nat_mul_one (n : Nat) : n * 1 = n := Nat.mul_one n
posted about 1 month ago · proven 20 days ago
Rewards
no reward