Um, Putin, that's absurd.
Subjectively, with respect to a particular person, everything is belief. Let's take the Pythagorean theorem since you bring it up. I believe in the Pythagorean theorem. Let's say A doesn't. I'm perfectly happy to say that his belief is a belief, and my belief is a belief.
Now, my belief happens to be true, and in my case justified, so it also counts as knowledge, but it is certainly -- among other things -- a belief. To refuse to use that word about something just because it is known to be true is an utterly ridiculous and completely indefensible position.
I believe in the Pythagorean theorem. I have incredibly strong reasons for doing so.
A in my earlier example believes in evolution. He does not have strong reasons for doing so (EVEN THOUGH STRONG REASONS MAY EXIST).
Let's see if you can follow the following example.
John is young and very ignorant. He is walking through the woods one day when he meets a man wearing a strange cloak and carrying an odd sack. The man tells him that he is an oracle and a wizard, and that he can tell John the truth about anything. John asks, "Is the pythagorean theorem true?" The man says, "Yes it is."
So, John now believes the Pythagorean theorem. _But he believes it for terrible reasons._ Just because WE happen to know for GOOD reasons that it is true, we are not going to use some word other than "belief" to describe his cognitive attitude toward it. We will not even call it knowledge, in this case, because his belief is entirely without good justification.
This is all very elementary philosophy, and also, for that matter, very elementary English language. None of it is controversial.