How do you  find secant lines?
 The following applet can be used to approximate the slope of the curve y=f(x) at x=a. Simply enter the function f(x) and the values a and b. The applet automatically draws the secant line through the points (a,f(a)) and (b,f(b)). As b approaches a, the slope of the secant line approaches the slope of the line tangent to f(x) at x=a. By selecting h= instead of b=, the applet automatically draws the secant line through the points (a,f(a)) and (a+h,f(a+h)). 