Figure \PageIndex9: (Left) If we wanted to measure the distance between two points on a cylindrical surface we would have to know the size of the cylinder in addition to the (x,y) coordinates of...Figure \PageIndex9: (Left) If we wanted to measure the distance between two points on a cylindrical surface we would have to know the size of the cylinder in addition to the (x,y) coordinates of the individual points. (Right) Despite having a radius and looking curved, by our definition the cylinder has a flat geometry because it can be unrolled onto a flat surface Credit: NASA/SSU/Aurore Simonnet