The Calculus Primer (2011)

Part VII. Differentials

Chapter 26. USING DIFFERENTIALS

7—5.Differential Notation. The standard formulas for differentiation can now be expressed in differential notation, as given below. For example, instead of writing

The relation, “the derivative with respect to x of a constant equals zero,” may also be stated as “the differential of a constant equals zero.”

Similarly,

becomesd(u + v) = du + dv.