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 



Graphing the Derivative of a Function
The following applet can be used to draw a graph of the derivative of f(x). Simply enter the function f(x) and the point of tangency, a. The applet automatically draws the graph of f(x) (in black) and the line tangent to f(x) at x=a. The slope of the tangent line is displayed in the lower left corner of the screen and plotted on the graph (red dot). As you move the point of tangency (green dot), the applet plots the slope of each tangent line, thereby drawing a graph of the derivative of f(x) (in red). If you have a guess as to what the derivative of f(x) is, then enter this function as f'(x) and the applet will draw the graph of f'(x) (in gray) so that you can compare the two graphs. 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. 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.
© 2011 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 