How to use this applet:

First, choose a topic from the buttons on the right of the applet.

The topic interfaces will typically require you to draw a line on the graph by dragging the mouse over it.

After you have chosen a line (two in the case of the Intersection topic), you can ask for the answer or find out how the answer was calculated.

The navigation buttons (Forward and Back) at the bottom of the applet allow you to move from one step to another in the explanation.

To return to the start of the applet, either press the back button until the beginning is reached, or use the refresh button in the web-browser.

Notes on the maths used in the applet: