Properties of Functions (cont)

Let f be a function from S1 to S2.

If no two elements of S1 are paired with the same element of S2 then f is said to be “one-to-one”. (It’s also said to be a injection.)

With S1 = { a, b, c} and S2 = { 1, 2}.

and f1 = { (a, 1), (b, 1), (c, 2) },

f1 is not one-to-one, since a and b are both paired with 1.

Let f5 = { (a, 1), (b, 2)} with domain { a, b}. f5 is one-to-one.

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