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theorem proved term proof

tetra_cos_eq

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formal statement (Lean)

  95theorem tetra_cos_eq : Real.cos tetrahedralAngleRadians = -1/3 := by

proof body

Term-mode proof.

  96  rw [tetrahedralAngleRadians]
  97  apply Real.cos_arccos
  98  · norm_num
  99  · norm_num
 100
 101/-- cos(2π/3) = -1/2 -/

depends on (1)

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