English
For any base b and n, log(b, n) = 0 if and only if n < b or b ≤ 1.
Русский
Для любых b, n: log_b(n) = 0 тогда и только если n < b или b ≤ 1.
LaTeX
$$$\\log_b(n) = 0 \\iff n < b \\ \\lor\\ b \\le 1.$$$
Lean4
@[simp]
theorem log_eq_zero_iff {b n : ℕ} : log b n = 0 ↔ n < b ∨ b ≤ 1 :=
by
rw [log, dite_eq_right_iff]
simp only [Nat.add_eq_zero_iff, Nat.one_ne_zero, and_false, imp_false, not_and_or, not_le, not_lt]