If cartesian product of A and B is equal cartesian product of C and D, then A equals C or B equals D. Write proof or give counterexample.

[pojler]

Hi!
I have a hard time solving this problem. I think that this is true, but I don't have a clue how to write a proof on this.

 

[Dr.Peterson]

Hi!
I have a hard time solving this problem. I think that this is true, but I don't have a clue how to write a proof on this.

What is the Cartesian product of A and B? What is the Cartesian product of C and D?

You might try proving it by contradiction.