English
If P and Q are equivalent and x = u, y = v, then ite P x y = ite Q u v.
Русский
Если P и Q эквивалентны и x = u, y = v, то ite P x y = ite Q u v.
LaTeX
$$$\text{If } P \iff Q, \ x = u, \ y = v \Rightarrow \operatorname{ite} P x y = \operatorname{ite} Q u v$$$
Lean4
theorem if_congr (h_c : P ↔ Q) (h_t : x = u) (h_e : y = v) : ite P x y = ite Q u v :=
if_ctx_congr h_c (fun _ ↦ h_t) (fun _ ↦ h_e)