Properties of Functions

Let f be a function from S1 to S2.

If every element of S2 appears as the second element of some ordered pair in f, then f is said to be “onto”. (It’s also said to be a surjection.)

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

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

f1 is onto.

Let f4 = { (a, 1), (b, 1), (c, 1) } with the same domain and range. f4 is not onto.

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