The applet on this page will be useful to us later, but right now we are going to use only a small amount of its capability.

We are going to use this applet to see whether or not the y-coordinate of a function approaches a number as x approaches some particular number.

Scroll down to read instructions.

Entering Functions

Press "New Function" button and type in a formula to be graphed in standard mathematical notation (e.g., "sin(x)", "e^(-x/10)"). The only variable the formula can use is x. You can add as many functions as you like, and "Delete Function" deletes the last one you entered.

Secant Lines & Slope

Click on the box that says "show slope of secant line". Click on the curve to mark a point on the curve. Click on a second point on the curve, and you should see the straight line (secant line) joining them, and the slope of that line. As you drag either one, the line and its slope change . Note that if the two nodes coincide, then the displayed slope is "undefined". This does not mean that the tangent line has no slope at that point. What does it mean?
If the slope is negative, the negative sign is printed rather short, so it is easy to miss. Be careful!

Erasing

If you want to erase one or both nodes, draw out a box on the screen (as though you were going to zoom in -- see below) that encloses the nodes you wish to delete, and then press the "backspace" key.

Rescaling

This brings up a panel which you can use to edit the scale of the graph. The x variable runs between xMin and xMax, and the y values run between yMin and yMax. Use xScale and yScale to set the spacing of tick marks on the axes. If xScale or yScale is zero, the graph will have no tickmarks on that axis.

Zooming

You can change the scale of your picture quickly with "Zoom In", "Zoom Out" and "Zoom to Box". The first two zoom in or out around the center of the graph. If you click and drag on the graphing window, you can draw out a box, and Zoom To Box will zoom in to make that box fill the whole window.

The applet on this page was created by Professor John Orr and resides at the site http://www.math.unl.edu/~jorr/java/html/SecantGrapher.html.   Professor Orr is in the Department of Mathematics at the University of Nebraska at Lincoln.

Return to Lab sites:
Calculus I Lab I.1   or   Main Calculus Page.