# questions on sets

• Nov 6th 2009, 01:49 AM
1234567
questions on sets
can some one please help me with the following question:

Attachment 13709

thanks

1234567
• Nov 6th 2009, 02:36 AM
Plato
For the first consider: $\displaystyle A = \left\{ {1,2,4,6} \right\}\;\& \,B = \left\{ {1,2,3,5} \right\}$.

For the second one, what $\displaystyle A^2$ mean?
I have never seen it defined in a 'set' context.
• Nov 6th 2009, 02:44 AM
1234567
thanks got the help,

A^2 and B^2 means the following

let A={1,2} and B={3,4}

then A^2={{1,1},{1,2},{2,1},{2,2}}

B^2={{3,3},{3,4},{4,3},{4,4}}
• Nov 6th 2009, 03:23 AM
Plato
Quote:

Originally Posted by 1234567
A^2 and B^2 means the following
let A={1,2} and B={3,4} then A^2={{1,1},{1,2},{2,1},{2,2}}
B^2={{3,3},{3,4},{4,3},{4,4}}

It appears that you mean the cross product. But the notation is incorrect.
$\displaystyle A\times A=\{(1,1),(1,2),(2,1),(2,2)\}$.
• Nov 6th 2009, 03:51 AM
HallsofIvy
You might also want to think about the situation in which $\displaystyle A\cap B= \phi$.
• Nov 6th 2009, 09:27 AM
1234567
thanks for the help.