theorem
proved
term proof
closure_forces_golden_equation
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formal statement (Lean)
113theorem closure_forces_golden_equation (S : GeometricScaleSequence)
114 (h_closed : S.isClosed) : S.ratio ^ 2 = S.ratio + 1 := by
proof body
Term-mode proof.
115 -- Unfold the closure condition
116 unfold GeometricScaleSequence.isClosed at h_closed
117 unfold ledgerCompose at h_closed
118 unfold GeometricScaleSequence.scale at h_closed
119 -- h_closed : r^0 + r^1 = r^2
120 -- This simplifies to: 1 + r = r^2
121 simp only [pow_zero, pow_one] at h_closed
122 -- Rearrange to r^2 = r + 1
123 linarith
124
125/-- **THEOREM**: The unique positive closed ratio is φ.
126
127Combining with the previous theorem: the only positive ratio that
128makes a geometric scale sequence closed is φ = (1 + √5)/2. -/