The real number system
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1.2 The real number system (EMA3)
We use the following definitions:

\(\mathbb{N}\): natural numbers are \(\left\{1; 2; 3; \ldots\right\}\)

\(\mathbb{N}_0\): whole numbers are \(\left\{0; 1; 2; 3; \ldots\right\}\)

\(\mathbb{Z}\): integers are \(\left\{\ldots; 3; 2; 1; 0; 1; 2; 3; \ldots\right\}\)
The following video shows an example of determining which of the above sets of numbers a particular number is in.
Not all numbers are real numbers. The square root of a negative number is called a nonreal or imaginary number. For example \(\sqrt{1}\), \(\sqrt{28}\) and \(\sqrt{5}\) are all nonreal numbers.
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Rational and irrational numbers
