ABSTRACT
Definition 4.1 (Derivative at a point). Let f be a function defined on an open interval I , and let a be a point in I . We say f is differentiable at a, with derivative f ′(a), if the limit
f ′(a) = lim x→a
f(x)− f(a) x− a
exists.
Definition 4.1 (Derivative at a point). Let f be a function defined on an open interval I , and let a be a point in I . We say f is differentiable at a, with derivative f ′(a), if the limit
f ′(a) = lim x→a
f(x)− f(a) x− a
exists.