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Homework Help: 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
    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


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    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


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    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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