Inwords: Ifwechangexbyanamountdx,then/ehangesbyanamountdf;thederivative
is the proportionality factor. Fot example. in Fig. 1.17(a),the function varies slowly with
x, and the derivative is correspondingly small. In Fig. l.l7(b), / inereases mpidly with x,
and the derivative is large, as you move away from x = 0.
Geomctrical Interpretation: The derivativedf /dx istlte slope of the graph of / versus x.