Differential calculus 

You mentioned that you "disagree with some of these changes, mostly as a matter of style", however, the changes are not meant to be stylistic, they are meant to be more accurate.  Eg. saying that differential calculus is "concerned with the study of the rates at which quantities change" is rather vague, as it makes no mention of the interval over which the change is measured.  Compare to, for example:
http://mathworld.wolfram.com/Derivative.html .  Any objections to reverting to my changes?