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: Subsets - analysis

  1. Feb 6, 2010 #1
    1. The problem statement, all variables and given/known data

    I need to find out whether the subset Re(real no's) of complex no's is open, closed or neither.

    2. Relevant equations



    3. The attempt at a solution

    Im not really sure how to begin this...any help please?
     
  2. jcsd
  3. Feb 6, 2010 #2

    HallsofIvy

    User Avatar
    Science Advisor

    Let x be any real number and consider a neighborhood of it in the complex numbers: [itex]\{z | |z- x|< \delta\}[/itex]. Does that contain any non-real numbers?
     
  4. Feb 7, 2010 #3
    yes i think it does contain non real numbers, so this would imply that it is an open subset?
    how would i go about sketching it?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook