English
Group homomorphisms preserve inverses: f(a^{-1}) = f(a)^{-1} for all a.
Русский
Гомоморфизмы групп сохраняют обратные: f(a^{-1}) = f(a)^{-1} для всякого a.
LaTeX
$$$f(a^{-1}) = f(a)^{-1} \\quad( a\\in \\mathrm{Group} ).$$$
Lean4
/-- Group homomorphisms preserve inverse. -/
@[to_additive /-- Additive group homomorphisms preserve negation. -/
]
protected theorem map_inv [Group α] [DivisionMonoid β] (f : α →* β) (a : α) : f a⁻¹ = (f a)⁻¹ :=
map_inv f _