1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Confusion about the boundary of a simple set

  1. Aug 31, 2014 #1

    Nathanael

    User Avatar
    Homework Helper

    1. The problem statement, all variables and given/known data

    Determine the boundary of the following set. As usual, z=(x,y).

    [itex]0<\left| z-z_0 \right|<2[/itex]

    2. The attempt at a solution

    The book's solution says "The circle [itex]\left| z-z_0 \right|=2[/itex] together with the point (0,0)"

    Why should the answer not be "... together with the point [itex]z_0[/itex]"?
     
  2. jcsd
  3. Aug 31, 2014 #2

    Mark44

    Staff: Mentor

    The book's answer seems incorrect to me. The original inequality represents all of the points inside (but not on) the circle of radius 2 with center at z0, not including this center point.
     
  4. Aug 31, 2014 #3

    HallsofIvy

    User Avatar
    Science Advisor

    Yes, that was clearly a typo.
     
  5. Sep 1, 2014 #4

    Nathanael

    User Avatar
    Homework Helper

    Thank you both, it's my first time learning these ideas (even if they are fairly simple) so I just wanted to make sure I wasn't misunderstanding.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Loading...