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Math help!! URGENT

Discussion in 'Homework Help' started by MohtasaUnique, Feb 17, 2011.

  1. MohtasaUnique

    MohtasaUnique Grand Master
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    Math help!! URGENT

    So I've got a makeup test to turn in tomorrow, and I need help with a few questions. I'd post in the homework help section, but apparently, I don't have the permissions to...(?)

    Anyway, here's the problems, if you can solve any or all of them, I'd greatly appreciate it!

    Find all solutions of the given equations:

    #1:
    2cos²x-cosx-1=0
    After using the quadratic equation, I come up with cosx=1 OR -1/2
    What do I do next?


    #2:
    cos5t=1/2
    No idea what to do with this :[
     
  2. Relevance

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    Math help!! URGENT

    cos(x) = 1,-1/2

    If you have calculator
    use inverse cos on on both sides (cos^-1) and solve.

    If you don't, you have three ways. Unit circle and logic, memorization, or method of 30 60 90 and 45 45 90 triangles. Since you're in a hurry, looks like you'll need memorization.

    http://www.mathplusfun.com/Content/Guide/Trigonometry/tri3b.gif
     
  3. Dragon kid

    Dragon kid Active Member
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    Math help!! URGENT

    in the first question take : cosx as t.
    so it becomes t.t.x.x+tx-1 ,,
    use quadratic formula :
    x= -b+rootD upon 2a and
    x= -b - rootD upon 2a,

    where a=t.t
    b=t
    c=1
    D= b.b-4ac
    when u"ll get 2 vales substitute t and u"ll get the answer :D

    in second question we know that,
    cos60=1/2
    we are given,
    cos5t=1/2

    5t=60
    so, t is 20degrees ,

    thx , if i could help :D
     
  4. Koot

    Koot Forum Addict

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    Math help!! URGENT

    If 5t=60, then t=12 not 20. Probably a typo incase you didn't catch it.

    If they ask for all values of that satisfy that with no given range then the answer would look like

    (degrees) + kpi, where k is any integer.

    This varies from each trig function, not even sure if just pi is even right for any one of though.
     
  5. MohtasaUnique

    MohtasaUnique Grand Master
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    Math help!! URGENT

    I solved it, thanks for the help broskis! :]
     
  6. rebecca520

    rebecca520 Newcomer
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    Math help!! URGENT

    lol, your funny, congratulations
     
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