mon=f(r) sec f(x+△x) △y=f(x+△x)-f(x) f(r) x+△x △ f(x)= lim dy FIGURE 3. 9 Ax→0 △xdx Copyright@2011 Pearson Education, Inc. Publishing as Pears on Addison-Wesley Slide 3-15Copyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Slide 3 - 15