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lemma proved tactic proof

phi_pow_ge_one

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formal statement (Lean)

  54lemma phi_pow_ge_one (n : ℕ) : 1 ≤ phi ^ n := by

proof body

Tactic-mode proof.

  55  induction n with
  56  | zero => simp
  57  | succ k ih =>
  58    have : phi ^ (k + 1) = phi ^ k * phi := pow_succ phi k
  59    rw [this]
  60    calc 1 = 1 * 1 := by ring
  61      _ ≤ phi ^ k * phi := by
  62          exact mul_le_mul ih (le_of_lt one_lt_phi) (by norm_num) (by positivity)
  63
  64/-- φ^m < φ^n when m < n. -/

used by (4)

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depends on (6)

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