Finding the Foci of an Ellipse From an Equation

Learning Resource Type

Classroom Resource

Subject Area

Mathematics

Grade(s)

9, 10, 11, 12

Overview

In this instructional video and practice activity from Khan Academy, students will explore how the radii and the foci of an ellipse relate to each other and how this relationship can be used to find the foci from the equation of an ellipse. This video can be used during a lesson on solving systems of equations. The video is 13 minutes and 48 seconds in length and can be assigned through Google Classroom. There are practice problems included after the video.

Khan Academy is a free resource for teachers. Teachers can sign up for a free account to access additional resources.

Mathematics (2019) Grade(s): 09-12 - Precalculus

MA19.PRE.31

Graph conic sections from second-degree equations, extending from circles and parabolas to ellipses and hyperbolas, using technology to discover patterns.

UP:MA19.PRE.31

Vocabulary

  • Hyperbola
  • Ellipse
  • Degenerate conic
  • Focus (foci)
  • Latus rectum (focal distance)
  • Major axis (transverse axis)
  • Minor axis (conjugate axis)
  • Eccentricity
  • Asymptote
  • Directrix
  • Locus

Knowledge

Students know:
  • Vertex form of a parabola.
  • Standard form of a circle.
  • Vertex and axis of symmetry of a parabola.
  • Completing the square.
  • Factoring a quadratic function.

Skills

Students are able to:
  • Graph equations of parabolas.
  • Graph equations of circles.
  • Graph equations of ellipses.
  • Calculate eccentricities of ellipses.
  • Graph equations of hyperbolas.
  • Classify a conic section using its general equation and/or its discriminant.

Understanding

Students understand that:
  • A conic section is a graph of an equation of the form Ax2 + Bxy + Cy2 +Dx +Ey + F = 0.
  • The only conic sections that are functions are parabolas that open upward or downward, previously learned as quadratic functions and hyperbolas that are written in the form of a rational function.
  • Using algebra to manipulate the equation of a conic section, particularly the method of "completing the square"" can be used to determine the parts and properties of its graph

CR Resource Type

Audio/Video

Resource Provider

Khan Academy

License Type

Custom
ALSDE LOGO