[header] How to understand euclidean geometry [title] Learn postulate 1-a line segment can be formed by joining any two points. [step] If you have two points, a and b, you can draw a line segment connecting those two points. Only one line segment can ever be made by connecting the two points.
[title] Know postulate 2-any line segment can be extended toward infinity in either direction. [step] Once you have constructed a line segment between two points, you can extend this line segment into a line.