Differential Calculus for Beginners

From the INTRODUCTION. The branch of Mathematics called the Differential Calculus was originally invented by Sir Isaac Newton, and later independently by Leibnitz, for the purpose of dealing with variable quantities; that is to say, with any quantity which does not remain constant, of which kind of quantity the whole of Physics and Engineering and daily life is full. For in so far as things remain constant they are stagnant; every kind of activity involves variable quantities, and therefore...