Work out how to make two multiple lines add head to tail continuously in C (WinAVR for Teensy microcontroller)

The project is probably very simple, however I have spent the last 12 hours on it and haven't gotten anywhere. I have written a function that draws 10 lines end to end with increasing angle so it forms a curve. I want to get the x and y positions from the end of the 10th line, then set this as the new starting coordinates for a second set of 10 lines so I always have at least 10 lines on the screen at a time. I have written 1 for loop for the first ten lines, and passed the last x and y coordinates for the 10th line to another for loop which uses that as the starting coordinates for a second set of 10 lines. The problem is, I cannot then pass the last x and y coordinates from the second for loop to be used as the starting point for the first again. I have tried everything and the first for loop refuses to draw if I force it to use values that are derived originally from itself. The project is very small, but you will be required to install WinAVR, GCC compiler and some C libraries. I have budgeted $100 for the help.