Tangent and secant slopes

Calculus consists of those problems in mathematics that can be solved with the following basic approach:
Approximate and take a limit!
The simplest, standard, geometric example of this process is the approximation of the slope of a tangent line with a secant line. Here's an illustration of this basic idea.
Choose $f$: $f(x)=x^2$ $f(x)=\frac{1}{3}e^x$ $f(x)=\sin(2x^2)+x/4$
Show secant line
$h = $
secant slope =
tangent slope =