1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Geometry Coordinate

  1. Aug 22, 2007 #1
    1. The problem statement, all variables and given/known data
    Given that Z is a complex number with condition |Z-1|+|Z+1|=7

    Illustrate Z on Argand Diagram and write out the equation of Locuz Z

    I attempted to figured out the equation of locus Z,
    [tex]\sqrt{}[(x-1)^2+y^2][/tex] + [tex]\sqrt{}[(x+1)^2 + y^2][/tex] = 7
    [tex]\sqr{}x^2 + 1 - 2x + y^2 + x^2 + 1 + 2x + y^2 = 49[/tex]
    [tex]\sqr{}2x^2 + 2y^2 = 47[/tex]

    it's not necessary the correct answer though...
    however, I can't figure how to illustrate the diagram! help!
  2. jcsd
  3. Aug 22, 2007 #2
    Assuming that your calculations are correct, that gives a circle of radius [tex]\sqrt{47/2}[/tex]. However, I don't think it is... Check your algebra carefully -- squaring both sides doesn't mean get rid of square roots!

    Another way to think about it is that the original equation says that the distance from a point on the locus to the points +1 and -1 add up to 7. This is the condition for an ellipse with its foci at -1 and 1! And an ellipse is only a circle if the foci coincide.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Geometry Coordinate
  1. Coordinate Geometry (Replies: 1)

  2. Coordinate geometry (Replies: 1)

  3. Coordinate geometry (Replies: 9)

  4. Coordinate geometry (Replies: 2)

  5. Coordinate geometry (Replies: 1)