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theorem proved tactic proof

wallpaperJ_pos_of_ne_one

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formal statement (Lean)

 165theorem wallpaperJ_pos_of_ne_one {g : WallpaperGroup}
 166    (h : symmetryRatio g ≠ 1) : 0 < wallpaperJ g := by

proof body

Tactic-mode proof.

 167  unfold wallpaperJ
 168  have hx_pos : 0 < symmetryRatio g := symmetryRatio_pos g
 169  have hx_ne : symmetryRatio g ≠ 0 := ne_of_gt hx_pos
 170  rw [Cost.Jcost_eq_sq hx_ne]
 171  have h_sq_pos : 0 < (symmetryRatio g - 1) ^ 2 := by
 172    have h_diff : symmetryRatio g - 1 ≠ 0 := sub_ne_zero.mpr h
 173    positivity
 174  have h_den_pos : 0 < 2 * symmetryRatio g := by linarith
 175  positivity
 176
 177/-- The trivial-symmetry group `p1` has strictly positive J-cost. -/

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