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Trig Test Question

  1. Dec 17, 2008 #1
    1. The problem statement, all variables and given/known data
    tana^2 = sin2a


    2. Relevant equations



    3. The attempt at a solution
    i set tana^a = sec^2a -1
    sec^2 -1 = 2sinacosa

    didnt know where to go from here <_<
     
    Last edited: Dec 17, 2008
  2. jcsd
  3. Dec 17, 2008 #2
    do u want to show that [tex]tan(a^2)=sin(2a)[/tex] or what?
    and also is the problem like i wrote here or it should be sth like this:[tex](tana)^2=sin(2a)[/tex]

    ??

    p.s use more parentheses they don't hurt.
     
  4. Dec 17, 2008 #3
    its the second way
    [tex](tana)^2=sin(2a)[/tex]
    and i need to find values for x
    for example pi/4 pi/6 answers wont be like that but yea
    its not a proof
     
  5. Dec 17, 2008 #4

    jgens

    User Avatar
    Gold Member

    Alright, if you're aiming for solutions, try rearranging/reexpressing the equation so it satisfies the zero product property.

    Hint: reexpress (tan(a))^2 in terms of sine and cosine, and reexpress the sin(2a) in terms of cos(a) and sin(a).
     
  6. Dec 17, 2008 #5
    well i did
    didnt work
    trust me ive been on this for an hour and yeah ive tried to set it equal to zero
     
  7. Dec 17, 2008 #6

    jgens

    User Avatar
    Gold Member

    It should be fairly simple if you're familiar with elementary algebraic operations. You need to show what you're trying if you want help.
     
  8. Dec 17, 2008 #7
    well ok
    i did
    sinx^2/cosx^2 = 2sinxcosx
    then brign right hind side to left hand side, at the end it comes out to be
    sinx^2 - 2sinxcosx^3 = 0
    then sin facotrs and sin x = 0
    but im still left with sinx - 2cos^3x
     
  9. Dec 17, 2008 #8
    close SOLVED
     
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