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A set could have as many entries as you would like.
It could have one entry, 10 entries, 15 entries, or even an infinite number of entries.
On the next page you'll find out that a set could even have no entries at all!
For example, in the above list the English alphabet would have 26 entries, while the set of
even numbers would have an infinite number of entries.
Each entry in a set is known as an element. We'll find out more about elements in the next section.
Sets are written using curly brackets ("{" and "}"),
with their elements listed in between.
For example the English alphabet could be written as {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z}
and even numbers could be {0,2,4,6,8,10,...}
(Note: the dots at the end indicating that the set goes on infinitely)
As you may have discovered in previous math journeys, mathematicians hate to write.
We have symbols for everything.
Therefore the notion of writing out statements like "a is an element of the alphabet" or
writing
"3 is not an element of the set of even numbers" is abhorrent to us.
Therefore we have the symbols Î and Ï.
Î means "element of" ; Ï means "not an element of"
So we could replace the previous statements with
a Î {alphabet}
and
3 Ï {Even numbers}
Now if we named our sets we could go even further.
Give the set consisting of the alphabet the name B, and
give the set consisting of even numbers the name C.
We could now write
a Î B
and
3 Ï C.
In the next two examples you will see these two symbols at work
Example 1 V is the set of vowels
e Î V (e is an element of the set of vowels)
f Ï V (f is not an element of the set of vowels)
Example 2 X is the set {1,3,5,7,9}
3 Î X (3 is an element of X)
4 Ï X (4 is not an element of X)