ELLIPSE
Construct the graph of an ellipse by its definition:
An ellipse is the set of all points on a plane whose distance from two fixed points F1 and F2 add up to a constant - PF1+PF2=COST.
a) draw a segment AB of four units and take a point C on it;
b) on the x-axis plot down two points F1 and F2 having coordinates (-1,0) and (+1,0);
c) draw a circumference centred in F1 and radius AC; then a circumference centred in F2 and radius CB; label P and G the intersection points between the two circumferences and then activate "traces"; connect P with the foci;
d) move C on the segment AB and you will get the graph of an ellipse.