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Math Help - trig graphs

  1. #1
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    Smile trig graphs

    solve these equations for 0< x<360

    a) sinx=0.4
    b)3cosx=0.9
    c)2sinx=-1
    d)5tanx+4=-2

    can any1 explain to me what to do plz??
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  2. #2
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    you'll need a calculator with inverse trig capability.

    what kind of calculator do you have?
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  3. #3
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    got a casio scientific calculator.
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  4. #4
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    I'm not familiar with the casio's operation, but the first thing to do is make sure the calculator is in degree mode.

    to solve sin(x) = 0.4, use the inverse sine feature to find x.
    calculate \sin^{-1}(0.4).
    you should get 23.57817... degrees.

    note that the calculator will only give you the first solution in quad I, there is another solution in quad II equal to 180 - 23.57817... = 156.4218... degrees.

    to solve 3cos(x) = 0.9, divide by 3 to get cos(x) = 0.3. calculate
    \cos^{-1}(0.3), you should get 72.5423... degrees.

    once again, note that the calculator will only give you the first solution in quad I, there is another solution in quad IV equal to 360 - 72.5423... = 287.4576... degrees.

    get the idea?
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