grammar - Using "of" before "whether" and general usage of "whether"

I was reading a mathematics text, and I came across a phrase which I thought was written incorrectly. There was a part of a sentence:

... it begs the question whether or not A=B.

and I feel this is incorrect, but I'm not sure. I think it should be written like this:

... it begs the question of whether or not A=B.

Or maybe there that's also incorrect, and there is a better form altogether? Maybe taking out the "or not" would make it even more correct, but I'm still not sure. My main problem is that I think there should be an "of" before the "whether" but I don't know why.

So, what is the correct form of this expression?

Answer

Both uses of the phrase are correct.

I would probably use the 'begs the question of whether or not A=B' as it flows better, but the 'or not' is superfluous really. Whether A+B only has two options, true or false, so the 'or not' doesn't really add anything to the phrase.