This is not part of my homework, but it can make my life much easier. I try to prepare the Excel file as instructed in the link, but I can not find information on how to get the correct value of Theta Dot. http://www.esm.psu.edu/courses/emch12/IntDyn/course-docs/Euler-tutorial/ I'm sorry that I ask the question, but I do not have classes in physics, and one of my teachers requires us to prepare a program imitating a pendulum. This excel I would like to be treated as a base, which later I move to the code. My question: What formula I should try to generate value assigned to a cell Theta Dot? I can not find it in the link, which I have enclosed. Thanks in advance!