theorem
proved
tactic proof
finCost_symm
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formal statement (Lean)
24theorem finCost_symm {m : ℕ} (x y : Fin m) : finCost x y = finCost y x := by
proof body
Tactic-mode proof.
25 by_cases h : x = y
26 · subst h
27 simp [finCost]
28 · have h' : y ≠ x := by intro hyx; exact h hyx.symm
29 simp [finCost, h, h']
30
31/-- The cyclic carrier size for the `k`th modular realization. -/