English
If either a ≠ 0 or s ≠ 0, then hurwitzZetaEven a s equals completedHurwitzZetaEven a s divided by Gamma(s).
Русский
Если либо a ≠ 0, либо s ≠ 0, то hurwitzZetaEven a s равно completedHurwitzZetaEven a s делённому на Gamma(s).
LaTeX
$$$\\forall a:\\text{UnitAddCircle},\\ \\forall s:\\mathbb{C},\\ (a \\neq 0 \\lor s \\neq 0) \\\\Rightarrow\\ hurwitzZetaEven(a,s) = \\frac{\\mathrm{completedHurwitzZetaEven}(a,s)}{\\Gamma(s)}.$$$
Lean4
theorem hurwitzZetaEven_def_of_ne_or_ne {a : UnitAddCircle} {s : ℂ} (h : a ≠ 0 ∨ s ≠ 0) :
hurwitzZetaEven a s = completedHurwitzZetaEven a s / Gammaℝ s :=
by
rw [hurwitzZetaEven]
rcases ne_or_eq s 0 with h' | rfl
· rw [Function.update_of_ne h']
· simpa [Gammaℝ] using h