What has been drawn?
Now, if we look carefully, we can
informally say it looks like we have part of a line. We’ll be able to identify its
formal name by looking at what’s happening at the end of this line drawn. We have two arrows. Now, these arrows tell us that this
line extends in both directions. In fact, it extends infinitely in
both directions. And so we recall that the formal
mathematical definition of a line is a straight set of points that extend infinitely
in both directions. And so we can say that, here, we
have a line.