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Goniomentric inequations

  1. Feb 28, 2013 #1
    Hello, how can I solve cos(7x) > cos(3x) and tan(x) > -3 ?

    I know in the second one x is greater than -arctan(3) but smaller than what?

    Thanks!
     
  2. jcsd
  3. Feb 28, 2013 #2

    tiny-tim

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    hi scientifico! :smile:

    arctan(∞) ? :wink:
     
  4. Feb 28, 2013 #3
    90° + k*180°
     
  5. Feb 28, 2013 #4

    tiny-tim

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    yes :smile:

    (and of course you'll need the same " + k*180° " for arctan(-3) )
     
  6. Feb 28, 2013 #5
    x < -arctan(3) + k*180° ?
     
  7. Feb 28, 2013 #6

    tiny-tim

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    that makes no sense :redface:

    you can't have one equation (or inequation) with a multiple-value k !
     
  8. Feb 28, 2013 #7
    270°+ k*180° < x < -arctan(3) + k*180°
     
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