PF001A · theorem body

square_lt_reflect

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

A witnessed strict inequality between natural squares reflects to their roots.

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(a · a,b · b) → Lt(a,b)

Every purple notation token opens its conservative definition. This reading surface never changes the unchanged intuitionistic kernel or confers checked-use authority.

Definitions used by this theorem

In the theorem statement

PD0002 Lt

In local proof propositions

none
Exact expanded first-order statement
forall a b. (exists k. k + S (a * a) = b * b) -> exists k. k + S a = b

Proof neighborhood

Direct theorem prerequisites

le_or_lt · Stable closed natural_square_monotone_expanded · Alpha closed lt_not_le · Stable closed

Direct theorem dependents

PF001I pythagorean_leg_strictly_below_hypotenuse PF001T pythagorean_positive_gap_orders_parameters

Definition-aware tactic body

Only propositions whose conservative expansion has been checked for exact first-order equivalence are compacted. Every changed line retains its immutable exact replay command.

Read the argument

Proof checkpoints

16 script commands · 4 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.

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 hlt
02Use earlier factsL4–5

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

  1. L4
    specialize le_or_lt b
  2. L5
    specialize le_or_lt a
03Separate the logical casesL6–7

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

  1. L6
    cases le_or_lt
  2. L7
    exfalso
04Use earlier factsL8–16

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

  1. L8
    specialize lt_not_le (a * a)
  2. L9
    specialize lt_not_le (b * b)
  3. L10
    apply lt_not_le
  4. L11
    exact hlt
  5. L12
    specialize natural_square_monotone_expanded b
  6. L13
    specialize natural_square_monotone_expanded a
  7. L14
    apply natural_square_monotone_expanded
  8. L15
    exact le_or_lt_left
  9. L16
    exact le_or_lt_right

Library-wide reading audit

Original defined command ledger · 16 lines
  1. 0001intro a
  2. 0002intro b
  3. 0003intro hlt
  4. 0004specialize le_or_lt b
  5. 0005specialize le_or_lt a
  6. 0006cases le_or_lt
  7. 0007exfalso
  8. 0008specialize lt_not_le (a * a)
  9. 0009specialize lt_not_le (b * b)
  10. 0010apply lt_not_le
  11. 0011exact hlt
  12. 0012specialize natural_square_monotone_expanded b
  13. 0013specialize natural_square_monotone_expanded a
  14. 0014apply natural_square_monotone_expanded
  15. 0015exact le_or_lt_left
  16. 0016exact le_or_lt_right