BT001N · Bertrand theorem

mul_lt_mul_succ_left_nonzero

Stable checked-use theorem · independently kernel verified

Multiplication by a nonzero left factor strictly increases across a successor step.

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

∀ c. ∀ a. ¬c = 0 → Lt(c · a,c · S a)

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

1 occurrences

In local proof propositions

none

0 occurrences

Exact expanded native-PA statement
forall c a. ~(c = 0) -> exists r. r + S (c * a) = c * S a

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

19 script commands · 14 reading checkpoints · 0 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 (1)
01Induction on cL1–3

Split the argument into the base and successor obligations. The induction hypothesis is available only in the successor branch.

  1. L1
    induction c
  2. L2
    intro a
  3. L3
    intro hc
02Separate the logical casesL4–4

Follow the explicit conjunction, disjunction, witness, or contradiction step recorded below.

  1. L4
    exfalso
03Use earlier factsL5–5

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L5
    apply hc
04Calculate and transport equalitiesL6–6

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L6
    refl
05Fix variables and assumptionsL7–8

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

  1. L7
    intro a
  2. L8
    intro hc
06Construct an explicit witnessL9–9

Supply the displayed value, then prove that it has the required property.

  1. L9
    exists c
07Calculate and transport equalitiesL10–10

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L10
    trans S (c + S c * a)
08Use earlier factsL11–11

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L11
    apply PA4
09Calculate and transport equalitiesL12–13

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L12
    trans S (S c * a + c)
  2. L13
    congr
10Use earlier factsL14–14

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L14
    apply add_comm
11Calculate and transport equalitiesL15–16

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L15
    trans S c * a + S c
  2. L16
    symm
12Use earlier factsL17–17

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L17
    apply PA4
13Calculate and transport equalitiesL18–18

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L18
    symm
14Use earlier factsL19–19

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L19
    apply PA6

Library-wide reading audit

Original defined command ledger · 19 lines
  1. 0001induction c
  2. 0002intro a
  3. 0003intro hc
  4. 0004exfalso
  5. 0005apply hc
  6. 0006refl
  7. 0007intro a
  8. 0008intro hc
  9. 0009exists c
  10. 0010trans S (c + S c * a)
  11. 0011apply PA4
  12. 0012trans S (S c * a + c)
  13. 0013congr
  14. 0014apply add_comm
  15. 0015trans S c * a + S c
  16. 0016symm
  17. 0017apply PA4
  18. 0018symm
  19. 0019apply PA6