English
The expression ite (P ∨ Q) a b equals ite P a (ite Q a b), given decidability of P and Q.
Русский
Выражение ite (P ∨ Q) a b равно ite P a (ite Q a b) при разрешимости P и Q.
LaTeX
$$$\ite (P \lor Q) a b = \ite P a (\ite Q a b)$$$
Lean4
theorem ite_or : ite (P ∨ Q) a b = ite P a (ite Q a b) := by by_cases hp : P <;> by_cases hq : Q <;> simp [hp, hq]