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theorem proved term proof

spatialRadius_ne_zero_iff

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formal statement (Lean)

 157theorem spatialRadius_ne_zero_iff (x : Fin 4 → ℝ) : spatialRadius x ≠ 0 ↔ spatialNormSq x ≠ 0 := by

proof body

Term-mode proof.

 158  unfold spatialRadius
 159  rw [Real.sqrt_ne_zero (spatialNormSq_nonneg x)]
 160
 161/-- Nonzero spatial radius is automatically positive. -/

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depends on (8)

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