Differentiability Fails to exist where a function as a…
Discontinuity, Cusp or Vertical Tangent
Difference Quotient
\frac{f(b) - f(a)}{b - a}
Definition of the derivative
\lim_{h \to 0} \frac{(x+h)^2 - x^2}{h}
\frac{d}{dx} \log_a(x) =
\frac{1}{x \ln(a)}