Education Technology

Precalculus: Focus/Directrix Definition of Conics
by Texas Instruments

Published on October 02, 2011

Objectives

  • Students will describe the relationship between the focus and the directrix associated with three types of conics.
  • Students will define parabolas, ellipses, and hyperbolas by their focus and directrix.

Vocabulary

  • parabola
  • ellipse
  • hyperbola
  • focus
  • directrix

About the Lesson

This lesson involves observing and describing relationships between the focus and the directrix of each conic: parabolas, ellipses, and hyperbolas.
As a result, students will:

  • Manipulate the focus and the directrix of a conic to observe the relationships between the focus, the directrix, and the conic.
  • Observe the effect of the relationship between the focus and the directrix on the shape of an ellipse or hyperbola.
  • Define a parabola, an ellipse, and a hyperbola, by their respective focus and directrix.