Mapping from Set to Ordinate of Cartesian Product is Injection

Theorem
Let $S$ and $T$ be sets such that $T \ne \O$.

Let $S \times T$ denote their cartesian product.

Let $t \in T$ be given.

Let $j_t: S \to S \times T$ be the mapping from $S$ to $S \times T$ defined as:


 * $\forall s \in S: \map {j_t} s = \tuple {s, t}$

Then $j_t$ is an injection.

Proof
It has been shown in Correspondence between Set and Ordinate of Cartesian Product is Mapping that $j_t$ is a mapping.

Now it is to be shown that $j_t$ is injective, that is:
 * $\forall s_1, s_2 \in S: \map {j_t} {s_1} = \map {j_t} {s_2} \implies s_1 = s_2$

We have that:

Hence the result.

Also see

 * Definition:Canonical Injection (Abstract Algebra) for an instance of this construct in the context of algebraic structures