DEFINITION The Derivative The derivative of f is the function f'(r)=lim f(x+ h)-f(r →0 h provided the limit exists. If f'(r)exists, we say f is differentiable at x. If f is differen tiable at every point of an open interval 1, we say that f is differentiable on 1 Copyright@2011 Pearson Education, Inc. Publishing as Pears on Addison-Wesley Slide 3-13Copyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Slide 3 - 13