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Math Help - Using Calc to find Inverse

  1. #1
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    Question Using Calc to find Inverse

    I'm using a Sci Calc to find Inverse functions... I have no problem with sin cos tan...But I can't seem to get the right answer to, Y=Cot^-1(-.92170128)....I enter it as Tan^-1(1/-.92170128) and get -.826120119....The answer is supposed to be 2.3154724.....Calc must be in Rad...Can anyone tell my what my mistake is
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  2. #2
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    Quote Originally Posted by Brndo4u View Post
    I'm using a Sci Calc to find Inverse functions... I have no problem with sin cos tan...But I can't seem to get the right answer to, Y=Cot^-1(-.92170128)....I enter it as Tan^-1(1/-.92170128) and get -.826120119....The answer is supposed to be 2.3154724.....Calc must be in Rad...Can anyone tell my what my mistake is
    You have to add pi to your answer. Your job now is to think about why .....
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  3. #3
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    My thought is the range restrictions (0,pi)... I need to add pi so the number falls within the range? Right path...?
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  4. #4
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    Quote Originally Posted by Brndo4u View Post
    My thought is the range restrictions (0,pi)... I need to add pi so the number falls within the range? Right path...?
    tan^{-1} of your calculator always gives you an answer in the range (-\pi/2;+\pi/2), but since tan has period \pi you may add any integral multiple of \pi to get all the other (infinitely many) angles for which \tan has the exact same value. - Therefore: add or subtract \pi as many times as necessary to get an angle in the required range.
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