Google Classroom
GeoGebraGeoGebra Classroom

Generating all conic sections

Geometric context:

  1. Consider a line f and a point C defined on that line. Let's draw a circle c with centre C and radius CR.
  2. Consider a point B on f, and point A on the circle. Reflect point A with respect to line f to determine point A'.
  3. Finally, we draw the lines AB and A'C; these lines intersect at D
Observe that the locus of point D when point A is moved across the circle describes a conic section. Observe what happens when you move the point B.

Questions:

  • What happens if B is within the segment EE'?
  • What happens if B is not in the segment EE'?
  • What happens if B is equal to E or E'?
  • What happens if B is moved far away to infinity along f?
Note: The segment EE' is equal to 4CR.