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Math Help - general solution

  1. #1
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    Question general solution

    find the general solution of:

    sin(2x+30)=cos3x
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by rionariona View Post
    find the general solution of:

    sin(2x+30)=cos3x
    what have you tried. it sees to me that applying the addition formulas is the way to go.
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  3. #3
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    Quote Originally Posted by rionariona View Post
    find the general solution of:

    sin(2x+30)=cos3x
    The addition formula and then the double angle formulae.

    Rewrite cos(3x) as cos(2x+x) if you have to derive it. If not google it
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  4. #4
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    i tried google nd couldnt get anything
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  6. #6
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    how do i get the general solution with that?
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  7. #7
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    Quote Originally Posted by rionariona View Post
    how do i get the general solution with that?
    \sin (2x+30) = \sin (2x) \cos (30) + \cos (2x) \sin (30)

    \cos (3x) = 4 \cos^3 (x) - 3 \cos (x)


    \sin (2x) \cos (30) + \cos (2x) \sin (30) = 4 \cos^3 (x) - 3 \cos (x)


    If you need more help please show what working you've done. I'm not prepared to do this question for you
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  8. #8
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    thank you so much for the help, this is the answer i have arrived at:

    sin(2x+30)=cos3x
    sin(2x+30)=sin(90-3x)
    5x=60+360.k
    x=12+72.k
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