# help with sets and logic

• May 13th 2011, 02:44 PM
Sneaky
help with sets and logic
I want to show if
|AxB|=|A|
what can we conclude about A and B, and justify it.

I have that

|AxB|=|A|
|A|•|B|=|A|
|B|=|A|/|A|
|B|=1
so the cardinality of B is 1

Is this ok?
• May 13th 2011, 02:56 PM
Plato
Quote:

Originally Posted by Sneaky
I want to show if
|AxB|=|A| what can we conclude about A and B, and justify it.
I have that
|AxB|=|A|
|A|•|B|=|A|
|B|=|A|/|A|
|B|=1
so the cardinality of B is 1

Once again, have you failed to state important bits of information?

Do you know that $A\ne \emptyset~?$
If not, you need to discuses that possibility.