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