David Little  
Mathematics Department Penn State University Eberly College of Science University Park, PA 16802 
Office: 403 McAllister Phone: (814) 8653329 Fax: (814) 8653735 email:dlittle@psu.edu 



The Chain Rule
The following applet can be used to illustrate how the chain rule applies to the derivative of f(g(x)) at x=a. Simply enter the functions g(x) and f(x) and the value a. The applet automatically draws the graphs of g(x), f(x) and f(g(x)). The appropriate line tangent to the graph is drawn in red. For g(x), the tangent line goes through the point (a,g(a)), for f(x), the tangent line goes through the point (g(a),f(g(a))) and for f(g(x)), the tangent line goes through the point (a,f(g(a))). The value of a can be changed by simply typing a new value, such as "1.2345", "pi/2", "sqrt(5)+cos(3)", etc. You may also change this value by using the up/down arrow keys or dragging the corresponding point left or right. To move the center of the graph, simply drag any point to a new location. To label the xaxis in radians (i.e. multiples of pi), click on the graph and press "controlr". To switch back, simply press "controlr" again. Here is a list of functions that can be used with this applet.
© 2007 David P. Little Download this applet for offline viewing (includes source code). The above applet uses the Java Math Expression Parser (JEP) developed by Singular Systems 