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WORKBOOK

EMPTY SET (NULL SET):
…………………………………………………………………………………………………………………………………………………………
……………………………………………………………..... if A =  then n(A) = ……

A={} is not an
Examples for empty set: empty set. A is a set

A   xx is an int eger , such that x  30  with one element
2
which is 
B   xx is a triangle whose two int erior angles measure 90  

DISCUSSION
I- Read the following expression. What do you think?

Table shows a one-to-one correspondence between counting numbers and integers. In this case,
mathematicians say that these two sets have the same cardinality. We think that these two sets
must be the same size. However, the fact is that all counting numbers are also integers.

Counting Numbers Integers

1 0

2 1

3 -1

4 2

5 -2

… …

Table: One to one correspondence between
counting numbers and integers.

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