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Thread: Trigonometric identity

  1. #1
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    Trigonometric identity

    How I solve the equation:
    sin2x + sinx = 2

    ?
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  2. #2
    MHF Contributor
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    Re: Trigonometric identity

    let $u = \sin(x)$

    solve the resulting quadratic.

    ensure the values obtained are valid and discard the invalid ones

    solve for $x$ via $x = \arcsin(u)$

    note that $\sin(x)$ is periodic and adjust the solution accordingly
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