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Math Help - arctan

  1. #1
    Boo
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    arctan

    Dear All!
    Pleas,e coudl someone help me to get
    f(x)=-pi/4 for x<1
    and
    f(x)=arctan2+arctan3 for x>1


    f(x)=arctan\frac{x+1}{x-1}+arctanx
    Many thanks!!!
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  2. #2
    Junior Member Barioth's Avatar
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    Re: arctan

    you have

    \\ \frac{-\pi}{4}= \arctan{\frac{(x+1)}{(x-1)}} +\arctan(x)\\
    you put Tan everywhere
    \\\tan\frac{-\pi}{4} = \frac{(x+1)}{(x-1)} +(x)\\-1 = \frac{(x+1)}{(x-1)} +(x)\\0 = \frac{(x+1}{x-1} +(x) + 1

    Solve the quadratic formula, you end up with x = 0 and x = (-1)
    Last edited by Barioth; January 16th 2013 at 11:00 AM.
    Thanks from Boo
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  3. #3
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    Re: arctan

    Quote Originally Posted by Barioth View Post
    you have

    \\ \frac{-\pi}{4}= \arctan{\frac{(x+1)}{(x-1)}} +\arctan(x)\\
    you put Tan everywhere
    \\\tan\frac{-\pi}{4} = \frac{(x+1)}{(x-1)} +(x)\\-1 = \frac{(x+1)}{(x-1)} +(x)\\0 = \frac{(x+1}{x-1} +(x) + 1

    Sorry about the <br/> I have no idea why these keep apearing :(
    As you can I got rid of the <br/> in your post.
    That happens if a linefeed in the code. This like this: <br />

    Your code should look like
    [tex]\\ \frac{-\pi}{4}= \arctan{\frac{(x+1)}{(x-1)}} +\arctan(x)\\[/tex]
    you put Tan everywhere
    [TEX]\\\tan\frac{-\pi}{4} = \frac{(x+1)}{(x-1)} +(x)\\-1 = \frac{(x+1)}{(x-1)} +(x)\\0 = \frac{(x+1}{x-1} +(x) + 1[/TEX]
    Thanks from Barioth and Boo
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  4. #4
    Junior Member Barioth's Avatar
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    Re: arctan

    Thanks for the info!
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  5. #5
    Boo
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    Re: arctan

    Hello!
    Many thanks!
    But, I should not know in advance that the result is pi/4! I have to calculate it...how?
    P.s. Please, can U tell me how did U got rid of arctans putting tan in front of arctan?
    Many thanks!!!
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