English
If x and y are self-adjoint in a semifield with involution, then their quotient x/y is self-adjoint.
Русский
Пусть x и y — самосопряжённые элементы в полуполе с инволюцией; entonces x/y остаётся самосопряжённым.
LaTeX
$$$\forall x,y\in R,\ IsSelfAdjoint(x)\to IsSelfAdjoint(y)\to IsSelfAdjoint\left(\dfrac{x}{y}\right)$$$
Lean4
theorem div {x y : R} (hx : IsSelfAdjoint x) (hy : IsSelfAdjoint y) : IsSelfAdjoint (x / y) := by
simp only [isSelfAdjoint_iff, star_div₀, hx.star_eq, hy.star_eq]