Exam-style question
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Explain the meaning of the notation domain → co-domain in the context of a function. Use ℕ → ℕ as an example, and state what the two occurrences of ℕ represent.
Model answer
What a good answer should say
- A function maps each value from one set, called the domain, to a value drawn from another set, called the co-domain.
- In ℕ → ℕ, the first ℕ is the domain, so the input values are natural numbers.
- The second ℕ is the co-domain, so the output values are drawn from the natural numbers.
Explanation
Why this works
The notation describes the direction of the mapping. The domain contains the possible input values, while the co-domain identifies the set from which output values are drawn.
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