Am doing self--study from the book : The Shape of Algebra in the Mirrors of Mathematics, by Gabriel Katz, Vladimir Nodelman; and have issues. Luckily, the concerned first chapter is freely accessible here. The s/w Visumatica basically is an openGL based one.
On pg.#5, question #1 is not clear in terms of logic implied, as need consider only one point to draw a rectangle and the other point is given by origin(0,0). So, how it is possible that some points are excluded. It is not stated that only first quadrant points are needed. So, the logic is not clear. Please help.
The image for the stated file of Visumatica is 
*Addendum * For the question #2 of the book on page #5-6, have files for Visumatica given as Ex 1.1-2a, Ex 1.1-2b, Ex 1.1-2c.
