Is Copying Homework Cheating?

That's actually a great thing though. Even if they have the answers, they don't have the way to get the answers. By knowing that, you might end up with a wrong answer through a wrong way, and instead of getting an F, you might get something better because you look in the book and notice "Hey, I haven't got the right answer. I must've done something wrong. Lemme check...".

This is actually what they are for. My high school maths teachers expected us to mark our own work with it. It was infuriating because half the time my answers would be different, but I'd have no bloody idea why because they don't include the working for obvious reasons.
Thinking about it now, aside from daily maths problems and maintaining science prac books, my high school never really set us regular homework....just essays and assignments. And even then, the maths homework often weren't checked and had no bearing on our grades, though you'd fail pretty hard come exam time if you didn't do them. So I've never had occasion to even think about copying, because it either wasn't worth anything, or would be so obvious that I'd get in trouble.