English
In a ordered semiring with zero less or equal to one and a strict positive multiplier, for any a > 0 we have a < 2a.
Русский
В упорядоченной полускольке с 0 ≤ 1 и положительным множителем, для любого a > 0 имеем a < 2a.
LaTeX
$$$0 \le 1 \Rightarrow \text{MulPosStrictMono}(R) \wedge a > 0 \Rightarrow a < 2a$$$
Lean4
theorem lt_two_mul_self [ZeroLEOneClass R] [MulPosStrictMono R] [NeZero (1 : R)] [AddLeftStrictMono R] (ha : 0 < a) :
a < 2 * a :=
lt_mul_of_one_lt_left ha one_lt_two