HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 236

The repetition of the first point is to ensure that the line forming the triangle is closed by connecting back to its starting point. The function formed by X2(T) and Y2(T) perform the same function with matrix M3. To use a different shape you need only change the points in matrix M2. If your new shape has more than three vertices you will need to change the TRange values in the PLOT SETUP view. It is not a good idea to use a shapes that is highly symmetrical, like a square, as it makes it harder to recognize transformations. Calculator Tip It is probably faster to have the class set it up themselves instead of sending it via cable or infra-red. Plus, if the class is not to regard this as 'magic' then it helps if they understand how the aplet works. This is best accomplished by having them set it up themselves. You might even consider allowing them to first play with drawing shapes of their own invention using a single matrix and only X1 and Y1. This will show clearly why the TRange settings are important, and how the values are extracted from the matrix. 236