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Math Help - inverse functions in equations

  1. #1
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    inverse functions in equations

    HI:
    Been racking my brains on this one for some time now:
    √3cotx+1=0

    i got: √3 X 1/tanx=-1
    then inverse to bring tanx onto top giving:
    tanx/√3=-1
    tanx=-1/√3
    which equals 60degrees, right? Which I thought I then apply to graph of tan.
    but apparently I need 120 and 300degrees

    thank you
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  2. #2
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    Quote Originally Posted by lemonz View Post
    HI:
    Been racking my brains on this one for some time now:
    √3cotx+1=0

    i got: √3 X 1/tanx=-1
    then inverse to bring tanx onto top giving:
    tanx/√3=-1
    tanx=-1/√3
    which equals 60degrees, right? Which I thought I then apply to graph of tan.
    but apparently I need 120 and 300degrees

    thank you
    \sqrt{3} \cot{x} + 1 = 0

    \cot{x} = -\frac{1}{\sqrt{3}}

    \tan{x} = -\sqrt{3}

    x = 120^{\circ}

    x = 120^{\circ} + 180^{\circ}= 300^{\circ}
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  3. #3
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    re: calculator problems?

    Hi:
    thanks skeeter:
    I have been struggling with this problem for some time now. The answer you gave was one of my solutions. But on my calculator, tan-1(-√3) gives a value of 60degrees, not 120degrees.
    Also, on my chart, √3 reads a value of 60degrees.
    I'm very confused now.
    I know how to use the calculator for these problems, and are getting correct results for other problems, but seem to be missing something here.
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  4. #4
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    Quote Originally Posted by lemonz View Post
    Hi:
    thanks skeeter:
    I have been struggling with this problem for some time now. The answer you gave was one of my solutions. But on my calculator, tan-1(-√3) gives a value of 60degrees, not 120degrees.
    Also, on my chart, √3 reads a value of 60degrees.
    I'm very confused now.
    I know how to use the calculator for these problems, and are getting correct results for other problems, but seem to be missing something here.
    your calculator does not say 60 degrees ... it says -60 degrees, doesn't it?

    -60 + 360 = 300

    300 - 180 = 120
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  5. #5
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    re: negative solutions

    Hi:
    I do get -60, your right.
    I should be working in the negative part of the tangent graph.
    I'm embarrassed. It seems that sometimes there is so much info. going in that one can miss, or mistake, the things one should know well enough.
    Thanks for pointing me in the right direction Skeeter.
    kind regards
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