This demo displays the line X(t) that you can alter in the
appropriately labeled textbox, the point (x0, y0) that you can move by
clicking and dragging, a segment with endpoints (x0, y0) and X(t0), and
a graph of the length of the segment with endpoints (x0, y0) and X(t)
as a function of t.

Change the value of t_{0} as in earlier demos.

As in earlier demos, there are "Show entire curve", "Show position
vector X(t0)" and "Show Color Spectrum" options.
"Show Color Spectrum" will also color the segment from (x0,y0) to X(t0),
and the graph of this distance.