English
The kernel of the quotient map induced by a congruence c on M is precisely c.
Русский
Ядро отображения, порождаемого конгруэнцией c на M, точно равно c.
LaTeX
$$$\ker (\,c.mk') = c$$$
Lean4
/-- The kernel of the quotient map induced by a congruence relation `c` equals `c`. -/
@[to_additive (attr := simp) /-- The kernel of the quotient map induced by an additive congruence
relation `c` equals `c`. -/
]
theorem mul_ker_mk_eq {c : Con M} : (mulKer ((↑) : M → c.Quotient) fun _ _ => rfl) = c :=
ext fun _ _ => Quotient.eq''