# Need help understanding very basic set theory

• March 21st 2010, 07:47 AM
matthayzon89
Need help understanding very basic set theory
1) 3 E {1,2,3}
2) 1 is not a subset of {1}
3){2} is not a subset of {1,{2},{3}}
4){1} is a subset of of {1,{2}}

I kind of understand the basics but am still lost when it comes to knowing how to read these in my head and understand what going on....

Thanks
• March 21st 2010, 12:48 PM
statman101
1) 3 E {1,2,3}
2) 1 is not a subset of {1}
3){2} is not a subset of {1,{2},{3}}
4){1} is a subset of of {1,{2}}

1. 3 is an element of the set
2. 1 is not a subset of the set, just an element
3. {2} is a subset of the set
4. {1} is not a subset of the set,
if the set were{{1},{2}} then {1} would be a subset of it
• March 21st 2010, 01:41 PM
Plato
Quote:

Originally Posted by statman101
1) 3 E {1,2,3}
2) 1 is not a subset of {1}
3){2} is not a subset of {1,{2},{3}}
4){1} is a subset of of {1,{2}}

1. 3 is an element of the set
2. 1 is not a subset of the set, just an element
3. {2} is a subset of the set
4. {1} is not a subset of the set,
if the set were{{1},{2}} then {1} would be a subset of it

statman101
If I read you correctly, the you missed 3 & 4.
$\{2\}\not\subseteq\{1,\{2\},\{3\}\}$ but this is true $\{2\}\in\{1,\{2\},\{3\}\}$.

$\{1\}\subseteq\{1,\{2\},\{3\}\}$ because $1\in\{1,\{2\},\{3\}\}$
• March 22nd 2010, 02:54 PM
matthayzon89