I tried plotting a "moving point" by putting the Plot command in a For loop and plotting the function of the index element. (The intention was to simulate a single point moving through the xy plane). I don't know why there is no output that I can see. However, when I try to Trace all the steps of Mathematica, I see that the plots are actually there but not displayed! So, I used Show and it still does not display. I want to know how to get around this problem. I will be grateful for any reply/conversation regarding this matter.