Yes, it should be "its" not "it's".

"Its" is a possessive pronoun, meaning "belonging to it." The confusion arises because if you don't substitute the pronoun "it" for the noun, an apostrophe is used. For example, the bone belonging to the dog is "the dog's bone." The eraser on the pencil is "the pencil's eraser." Both examples use an apostrophe plus an "s" in order to attribute ownership.

So other than my quickly typing the thread title what did you think of the theorum? Or did you only post to comment on the grammar? If so, then the lure worked.....muh ha ha ha.