Library
▹
Essentials
▹
Functions
Proposition 1.5.32.
Let
X
,
Y
be sets,
f
:
X
↔
Y
be a
bijection
. Then:
(
f
-1
)
-1
=
f
Proof.
f
-1
∘
f
=
id
X
by
definition of
f
-1
.