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 function

  1. May 14, 2005 #1
    I can only find two answers for this equation, whereas the books says it should be four. Can someone enlighten me? Showing the procedure would help:P

    (degrees)
    sec(2x+180) = 2 0<x<360
     
  2. jcsd
  3. May 14, 2005 #2

    Galileo

    User Avatar
    Science Advisor
    Homework Helper

    First write it as cos(2x+180)=1/2.

    Then get rid of the 180 (the 180 causes a shift in the graph of cos(2x)).
     
  4. May 14, 2005 #3

    OlderDan

    User Avatar
    Science Advisor
    Homework Helper

    Changing to cosine is a good idea, but you can't get rid of 180 and get the right answers for x. You could change the cosine to -cos(2x) = 1/2, or set the argument of the cosine as it stands to the values that have cosine = 1/2, then solve for x, keeping only the solutions in the specified interval.
     
  5. May 14, 2005 #4

    Galileo

    User Avatar
    Science Advisor
    Homework Helper

    That's what I meant by 'getting rid of the 180'.
     
  6. May 14, 2005 #5
    Check the range of x:
    0 < x < 360
    180 < 2x + 180 < 900
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook