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!

Reciprocal of a function

  1. Mar 2, 2007 #1


    User Avatar
    Gold Member

    Given the following graph:

    How can i sketch the reciprocal of that function? There are poles at x=-2 and x=2, so it means its reciprocal will have roots at -2 and 2 right? But thats not really enough information to compose a full sketch.

    How should i go about doing this?

  2. jcsd
  3. Mar 2, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    It's enough for a rough sketch. You can see that the function is symmetric about the y-axis so its reciprocal will be. You can see that at x= 0, the function has value just a little larger than -1 so its reciprocal will have value just a little less than -1. The reciprocal graph will start at x= 0, y= a little less than -1, rise to x= 2, y= 0, then continue increasing as x goes to + infinity. Use symmetry to get the graph for negative x.
  4. Mar 2, 2007 #3
    replace each y with 1/y for all x.
    eg. where y is tending to infinity, it should tend to 0.
  5. Mar 2, 2007 #4


    User Avatar
    Gold Member

    So it will be similar to a quadratic graph?
  6. Mar 2, 2007 #5
    the middle portion is very similar to graph of -sec x, so its reciproca would be similar to -cos x
  7. Mar 2, 2007 #6
    1/big = small

    1/small = big
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?