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Bijections.
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Functions.
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Injections.
Contents
Surjections.
Definition
2
.
3
.
1
A function
is a
surjection
(or
is surjective
) if every element of
has at least one pre-image in
.
is a surjection if, and only if:
Example
2
.
3
.
2
Proposition
2
.
3
.
3
Let
and
be two applications. If
and
are surjective, then
is a surjection.
Proposition
2
.
3
.
4
Let
and
be two applications. If
is surjective, then
is surjective.
Noah Dana-Picard 2007-12-28