lemma
proved
term proof
spatialNormSq_coordRay_spatial_1
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formal statement (Lean)
202private lemma spatialNormSq_coordRay_spatial_1 (x : Fin 4 → ℝ) (s : ℝ) :
203 spatialNormSq (coordRay x 1 s) = (x 1 + s) ^ 2 + x 2 ^ 2 + x 3 ^ 2 := by
proof body
Term-mode proof.
204 unfold spatialNormSq coordRay basisVec
205 rw [if_pos (rfl : (1 : Fin 4) = 1),
206 if_neg (by decide : (2 : Fin 4) ≠ 1),
207 if_neg (by decide : (3 : Fin 4) ≠ 1)]
208 ring
209