BT00PX · Bertrand theorem

le_mul_of_one_le_left

Alpha v34 checked-use theorem · independently kernel and Lean verified; not Stable

A factor at least one makes left multiplication extensive.

Current library: Alpha v34, 4,223 checked-use theorems; Stable remains 432. Historical first admissions, original proof editions, and non-admitted aliases are preserved. Exact original first-admission records.

Statement with defined notation

∀ a. ∀ b. Lt(0,a)Le(b,a · b)

Every purple notation token opens its conservative definition. Expanding the displayed statement recovers the exact first-order Peano-arithmetic formula checked by the unchanged kernel.

Definitions used by this theorem

In the theorem statement

2 occurrences

In local proof propositions

1 occurrences

Exact expanded native-PA statement
forall a b. (exists bpo_gap_left_factor. bpo_gap_left_factor + (1) = (a)) -> (exists bpo_gap_left_result. bpo_gap_left_result + (b) = (a * b))

Proof neighborhood

Direct theorem prerequisites

Direct theorem dependents

Definition-aware tactic body

Only local propositions introduced by have or suffices are compacted. Every changed line has an exact-AST conservative-expansion receipt; the kernel still receives the immutable original tactic script.

Read the argument

Proof checkpoints

12 script commands · 2 reading checkpoints · 1 local claims

This is a reading aid, not a new proof or a proof-tree certificate. Checkpoint groups are consecutive commands, not inferred branch boundaries. Every step links to the preserved script.

Definition notation is shown below. Open the paired exact edition for the original native formulas. Source pairing is not a new equivalence certificate.

Named ingredients (2)
01Fix variables and assumptionsL1–3

Work with arbitrary variables or the premises of the current implication.

  1. L1
    intro a
  2. L2
    intro b
  3. L3
    intro ha
02Establish hscaledL4–12

Establish this local claim before using it. It is not an additional assumption. The following proof commands apply mul le mul right.

  1. L4
    have hscaled : Le(1 · b,a · b)Definitions: Le(1 · b,a · b)Original native command in the exact edition
  2. L5
    specialize mul_le_mul_right 1
  3. L6
    specialize mul_le_mul_right a
  4. L7
    specialize mul_le_mul_right b
  5. L8
    apply mul_le_mul_right
  6. L9
    exact ha
  7. L10
    specialize one_mul b
  8. L11
    rewrite one_mul at hscaled
  9. L12
    exact hscaled

Library-wide reading audit

Original defined command ledger · 12 lines
  1. 0001intro a
  2. 0002intro b
  3. 0003intro ha
  4. 0004have hscaled : Le(1 · b,a · b)
    Exact native replay linehave hscaled : exists k. k + 1 * b = a * b
  5. 0005specialize mul_le_mul_right 1
  6. 0006specialize mul_le_mul_right a
  7. 0007specialize mul_le_mul_right b
  8. 0008apply mul_le_mul_right
  9. 0009exact ha
  10. 0010specialize one_mul b
  11. 0011rewrite one_mul at hscaled
  12. 0012exact hscaled