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: Inverse image and continuity

  1. Apr 1, 2008 #1
    1. a) Show that (f^-1 S)compliment = f^-1(S compliment) for any set S of reals.


    Then use part a) to show The function f is continuous iff f^-1(S) is closed for every closed set S.




    2. inverse image = f^-1(S) = {x: f(x) [tex]\in[/tex] S}
    f is continous iff for every open set U [tex]\in[/tex] the reals, f^-1(U) is open.
     
  2. jcsd
  3. Apr 1, 2008 #2
    part a is true for any set, so you need to show f^-1(S^c) = (f^-1(S))^c,

    so take x in f^-1(S^c), so f(x) is in S^c, so f(x) is not in S, so ...

    for part b, what have you tried and what is your definition of continuous, delta/epsilon?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook