[br]The right-hand side of this applet is a graph of the derivative function. As you use the slider [math]k[/math], note how the value of the derivative (slope of the tangent line) is modeled by the graph on the right.[br][br]As you use this applet you should focus on two main ideas: first, that the derivative of a function is itself a function, and second, that the graph of the derivative exists below the [math]x[/math]-axis when the slope of the tangent line is negative, exists above the [math]x[/math]-axis when the slope of the tangent line is positive, and crosses the [math]x[/math]-axis when the slope of the tangent line is zero.