HOW TO CONSTRUCT CONIC SECTIONS
Now is your turn to work. You have to follow these simple steps in order to obtain a conic by applying its definition.
a) Draw a straight line (DIRECTRIX) and a point F (FOCUS).
b) Take a point A on the directrix and trace the perpendicular line at this point;
c) Let V be the middle point of the segment FA;
d) Trace at any point above the focus F two parallel lines to the directrix;
e) Trace a circumference centered in F and having radius= d(dir,r1);
f) Trace a circumference centered in F and having radius= d(dir,r2), and plot the intersection points of each circumference and the parallel lines;
c) Draw the LOCUS THROUGH FIVE POINTS, passing the fours points and point V.
Now if you move the DIRECTRIX or the VERTEX V you can observe how the curve LOCUS represent a conic.