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Homework Help: Math - solving equation

  1. Sep 5, 2007 #1


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    [SOLVED] Math - solving equation

    1. The problem statement, all variables and given/known data

    x belongs to Real numbers

    2. Relevant equations

    solving on paper
    cos^2(x) - 4*cos(x) + (7 / 4 ) < 0

    3. The attempt at a solution

    no worthly attemps yet
  2. jcsd
  3. Sep 5, 2007 #2
    why don't you factorise it by using the completing the square thing or the ((-b)+or- (root(b^2) - 4ac) )/2a
    ...i think?
  4. Sep 5, 2007 #3


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    Science Advisor
    Homework Helper

    To follow up on sara_87's post, let z = Cos(x). Now you have a quadratic equation (inequality) which you can solve for z.

    Next time you have a similar question please post it under Pre-calculus Math.
  5. Sep 5, 2007 #4


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    Science Advisor

    Why in the world is this in "other Sciences"?
  6. Sep 7, 2007 #5


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    well, i didnt see simply 'math' section , only saw 'calculus math' , didnt see 'Precalculus Mathematics' since i didnt have much time to post, sorry for wrong section. Next time ill know where to post for these types of questions

    and btw, thx for your help, resolved it easily now
    Last edited: Sep 7, 2007
  7. Sep 7, 2007 #6


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    Staff: Mentor

    Thread moved to Precalc Math.
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