Thanks for that, it has helped a bit.
It is (0,-E1) i want the straight line(length 1 unit) to start at and (1,-E1) to be where the curve starts at the end of the line.
c1 := circle([D1, 0], R1);
This altered program is basically what I require except here the curve starts at (0,-E1) and not (1,-E1) as I need. When in that position it should give a continuous graph throughout.
Hope this is a little clearer