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

Cubic and Ellipse problem

  1. Nov 2, 2007 #1
    The question im looking at states:
    Prove that the elliptical function x^2 + 3y^2=b is orthogonal to the cubic y=3ax^3.

    I'm thinking they want me to prove if the functions are orthogonal when they intersect. If im correct that would just lead to;

    For the ellipse,
    2x+6y(m1)=0, m1=-x/3y, when they intersect: m1=-x/3(3ax^3)=-1/9ax^2

    Cubic,
    m2=9ax^2

    m1xm2=[-1/9ax^2][9ax^2]=-1, Therefore they are orthogonal when they intersect.

    Am I right here? Is this even what the question was asking for?
     
  2. jcsd
  3. Nov 3, 2007 #2

    HallsofIvy

    User Avatar
    Science Advisor

    Yes, that's exactly right.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook