Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Determining restrictions on an ellipse

  1. Mar 14, 2005 #1
    The equation [tex]Ax^2 + By^2 + Cx = 1 [/tex] represents an ellipse. If [tex]A > 0[/tex] and [tex]B > 0[/tex], what conditions must be satisfied if the ellipse has it's major axis on the y-axis?

    The answer is "[tex] C = 0[/tex] and [tex]A > B[/tex]"

    When I first wrote this question I thought [tex]A > B[/tex] should have been [tex]A < B[/tex]. So how do I figure out what the restrictions are? Why is [tex]A < B[/tex] wrong?
    Last edited: Mar 14, 2005
  2. jcsd
  3. Mar 14, 2005 #2
    Plot an ellipse where A > B and see if the answer is correct... then test your way of A < B.


    BTW: Your answer is correct. If B > A , then the major axis will run along the y-axis.
    Last edited: Mar 14, 2005
  4. Mar 14, 2005 #3


    User Avatar
    Science Advisor
    Homework Helper

    C different from zero would automatically shift the center of the ellipse from the center of coordinates...

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook