Points and lines in a plane
The following points describe some necessary ideas.
- A point either lies on a line or does not lie on a line.
- There is exactly one line passing through two distinct points.
- Two distinct lines in the plane either meet at a point or are parallel.
- Two lines in a plane are called parallel if they never meet, no matter how far they are produced (meaning extended). This is written AB || PG.
- Two lines parallel to a third line are parallel to each other.
- Three points that all lie on the one line are called collinear.
- Three lines that all pass through one point are called concurrent.