theorem
proved
term proof
phi_golden_recursion
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formal statement (Lean)
88theorem phi_golden_recursion : preferredAspectRatio * (preferredAspectRatio - 1) = 1 := by
proof body
Term-mode proof.
89 unfold preferredAspectRatio
90 have h : phi ^ 2 = phi + 1 := phi_sq_eq
91 have hphi : phi ^ 2 = phi * phi := sq phi
92 rw [hphi] at h
93 linarith [h]
94