Library
▹
Essentials
▹
Functions
Definition 1.5.4.
Let
X
,
Y
be sets,
f
:
X
→
Y
be a
function
,
S
⊆
Y
. We define:
f
-1
(
S
)
:
=
{
x
∈
X
:
f
(
x
)
∈
S
}
References.
https://en.wikipedia.org/wiki/Preimage