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Math Help - Trigonometric equations

  1. #1
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    Trigonometric equations

    Hello ! I cant remember how to solve this... please help me

    Find all the solutions in the intervall [-4pi; 4pi] for

    a) sin(x) = 0.23
    b) cos(x) = -0.9
    c) tan(x) < 1
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  2. #2
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    Quote Originally Posted by coobe View Post
    Hello ! I cant remember how to solve this... please help me

    Find all the solutions in the intervall [-4pi; 4pi] for

    a) sin(x) = 0.23
    b) cos(x) = -0.9
    c) tan(x) < 1
    (a) solutions are in quads I and II

    going from 0 to 4\pi ...

    x = \arcsin(.23) , \pi - \arcsin(.23) , 2\pi + \arcsin(.23) , 3\pi - \arcsin(.23)

    .. now you go from 0 to -4\pi

    (b) solutions are in quads II and III

    from 0 to 4\pi ...

    x = \arccos(-0.9) , 2\pi - \arccos(-0.9) , 2\pi + \arccos(-0.9) , 4\pi - \arccos(-0.9)


    get the idea?


    for (c) , look at the graph.
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