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Math Help - Trig Equation help

  1. #1
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    Trig Equation help

    hi I have a problem,

    sin^2x = 6(cosx +1)


    how do i solve and get answer pi/3, /3 etc.
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  2. #2
    Super Member 11rdc11's Avatar
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    Quote Originally Posted by cokeclassic View Post
    hi I have a problem,

    sin^2x = 6(cosx +1)


    how do i solve and get answer pi/3, /3 etc.
    1 - \cos^2{x} = 6(\cos{x} + 1)

    1 - \cos^2{x} = 6\cos{x} + 6

    0 = \cos^2{x} + 6\cos{x} - 5

    Can you finish up from here?
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  3. #3
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    Quote Originally Posted by cokeclassic View Post
    hi I have a problem,

    sin^2x = 6(cosx +1)


    how do i solve and get answer pi/3, /3 etc.
    Start by substituting \sin^2 x = 1 - \cos^2 x.

    Now re-arrange into a quadratic equation involving \cos x. Factorise and solve to get two equations for \cos x.

    The only equation that leads to real solutions is \cos x = 1.
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  4. #4
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    Ahh I had it right! I was looking at the wrong answer!
    Thank you very much
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