English
In a monoid, for any P and a ∈ M, a^{if P then 1 else 0} = if P then a else 1.
Русский
В моноиде для произвольного P и a ∈ M выполняется a^{if P then 1 else 0} = if P then a else 1.
LaTeX
$$$a^{\\mathrm{ite}(P,1,0)} = \\mathrm{ite}(P,a,1)$$$
Lean4
@[to_additive boole_nsmul]
theorem pow_boole (P : Prop) [Decidable P] (a : M) : (a ^ if P then 1 else 0) = if P then a else 1 := by
simp only [pow_ite, pow_one, pow_zero]