Tell me more ×  I'm trying to do this:  enter image description
here  In this graph, the secant points are aproximated in order
to become the tangent, it seems I need some kind of function
which plots a line based on two points and it's points do not
limit the end of the line.  This is what I could do, as you can
evaluate (see?), you'll see the line ends at the proposed
points.    Plot[{15 - 2 x^2}, {x, -1, 3}],   Graphics[Line[{{1,
13}, {2, 7}}]]  I've read the reference on line but I still have
no idea on how to do it, I imagine there are two ways of doing
it, (1) the way I did, with Line; (2) With the Plot function.
share|improve this question A Line[] object always has two ends,
by its very nature (so it is properly a line segment as opposed
to a line)... what you can do is to have your Line[] extend past
the PlotRange of your plot... –  Ｊ. Ｍ. Sep 15 '12 at 10:21 This
is a standard sort of thing folks do with Mathematica. Why not
look at versions published to the Wolfram Demonstrations
project, e.g.: – 