Hi,

I've a quick question about Borel algebra. The Borel algebra on setXis defined as the smallest σ-algebra containing all open sets (or, equivalently, all closed sets). Let R be the set of reals and B(R) denote the Borel algebra on R. Then my question is: whether B(R)*B(R) equals B(R^{2})? How do you prove or disprove this?

Thanks