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Trigonometric inequality

  1. Mar 21, 2009 #1
    1. The problem statement, all variables and given/known data
    solve the inequality:
    -1[tex]\leq[/tex] 1[tex]/[/tex](1+cosx) [tex]\leq[/tex]1

    3. The attempt at a solution

    firstly cosx does not equal -1 but you'll see doesn't help much
    -1<cosx<1
    0<cosx+1<2
    that makes the above equation 1/(1+cosx) between 0.5 and infinity. but I have no clue as to how to find the set of x which solve the inequality
     
  2. jcsd
  3. Mar 21, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi IsrTor! :smile:

    You need to learn your trigonometric identities …

    what does 1 + cosx also equal? :wink:
     
  4. Mar 21, 2009 #3

    Mark44

    Staff: Mentor

    Since 1/(1 + cosx) is between -1 and 1, its reciprocal has to be larger than 1 or smaller than -1, depending on whether 1/(1 + cos x) is positive or negative, respectively.

    Can you do something with that?
     
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