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Math Help - I don't undestand these trig angle questions at all.

  1. #1
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    I don't undestand these trig angle questions at all.

    Find theta, 0 < theta < 2pi, if tan theta= 0.66

    Find theta, 0 < (or equal to) theta < (or equal to) 360 if cos theta= -0.89

    Am I over-thinking these questions or does it actually have an extensive answer? To me, my guess is for 1, to do .66 tan-1 and for 2, to do -0.89 cos-1, but that seems to simple.
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  2. #2
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    Re: I don't undestand these trig angle questions at all.

    Quote Originally Posted by ChrisTurner91 View Post
    Find theta, 0 < theta < 2pi, if tan theta= 0.66
    Find theta, 0 < (or equal to) theta < (or equal to) 360 if cos theta= -0.89
    Am I over-thinking these questions or does it actually have an extensive answer? To me, my guess is for 1, to do .66 tan-1 and for 2, to do -0.89 cos-1, but that seems to simple.
    For the first there are two answers: \arctan(0.66)~\&~\arctan(0.66)+\pi.

    What are the two for the second part?
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    Re: I don't undestand these trig angle questions at all.

    arccos(-0.89) and arccos(-0.89) + pi?

    So I'm just using the inverse function to solve for it?
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    Re: I don't undestand these trig angle questions at all.

    Quote Originally Posted by ChrisTurner91 View Post
    arccos(-0.89) and arccos(-0.89) + pi?
    So I'm just using the inverse function to solve for it?
    No there is far more to it than that.
    First note that the question asks for the answer in degrees.
    So you must convert \arccos(-0.89) to degrees.
    That answer will be in quad-II.

    The second will be in quad-III with the same reference angle as the the first.
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