Here is Zona Land's graphic calculator, EZ Graph. The graphics for almost any polynomial, rational, exponential, logarithmic, or trigonometric function can be drawn with it. EZ Graph will allow you to enter variables into your function definition so that you can easily see the effect of changing the function's coefficients on the shape of the graph. You can zoom into an interesting part of the graph using a mouse drag and click. Also, coordinates on the graph can be identified with a mouse click. There's more to EZ Graph, so the help link below.
Click on this Help link or the help link below for a complete explanation.