theorem
proved
tactic proof
intensityAtRung_succ_ratio
show as:
view Lean formalization →
formal statement (Lean)
46theorem intensityAtRung_succ_ratio (k : ℕ) :
47 intensityAtRung (k + 1) = intensityAtRung k * phi⁻¹ := by
proof body
Tactic-mode proof.
48 unfold intensityAtRung
49 have hphi_ne : phi ≠ 0 := Constants.phi_ne_zero
50 have hzpow : phi ^ (-((k : ℤ) + 1)) = phi ^ (-(k : ℤ)) * phi⁻¹ := by
51 rw [show (-((k : ℤ) + 1)) = -(k : ℤ) + (-1 : ℤ) by ring]
52 rw [zpow_add₀ hphi_ne]
53 simp
54 have hcast : ((k + 1 : ℕ) : ℤ) = (k : ℤ) + 1 := by push_cast; ring
55 rw [hcast, hzpow]; ring
56