import Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex
import Mathlib.Tactic
/-!
# International Mathematical Olympiad 1961, Problem 3
Solve the equation
cosⁿ x - sinⁿ x = 1,
where n is a given positive integer.
-/
namespace Imo1961P3
open Real
/- determine -/ abbrev solutionSet (n : ℕ+) : Set ℝ := sorry
theorem imo1961_p3 {n : ℕ} {x : ℝ} (npos : 0 < n) :
x ∈ solutionSet ⟨n, npos⟩ ↔
(cos x) ^ n - (sin x) ^ n = 1 := sorry
end Imo1961P3
This problem has a complete formalized solution.
The solution was imported from mathlib4.