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Math Help - Trigonometric equation.

  1. #1
    Junior Member
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    Trigonometric equation.

    Is there something wrong with Latex or anything? I get a syntax error message every time I try to write the equation...

    Code:
    3\sin(2x)-4\cos(2x)=-2
    Gives: 3\sin(2x)-4\cos(2x)=-2

    Why?

    This makes it hard for me to show what I've done and get feedback on what Im doing wrong.
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  2. #2
    Super Member Matt Westwood's Avatar
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    There's been a problem with LaTeX recently on this site. Not sure if it's fixed yet, I'm still having intermittent trouble.
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  3. #3
    Super Member

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    Hello, MatteNoob

    3·sin(2x) - 4·cos(2x) .= .-2
    Divide by -5: . (0.8)cos(2x) - (0.6)sin(2x) .= .0.4

    Let: .cos(θ) = 0.8, . sin(θ) = 0.6 . . θ = arccos(0.8)


    We have: . cos(θ)cos(2x) - sin(θ)sin(2x) .= .0.4

    . . which becomes: . cos(θ + 2x) .= .0.4


    Then we have: . θ + 2x .= .arccos(0.4) . . 2x .= .arccos(0.4) - θ


    Therefore: . x . = . ½[arccos(0.4) - θ] . = . ½[arccos(0.4) - arccos(0.8)]

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