It is inevitable that your work with AutoLISP will involve some geometric manipulations. With the box program in chapter 2, you have already created a program that derives new point locations based on user input. There, you learned how to take coordinate lists apart, then re-assemble them to produce a new coordinate. In this chapter, you will be introduced to other AutoLISP functions that will help you determine locations in your drawings coordinate system and in the process, you will review some basic trigonometry.