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Thread: Inverse of a function help

  1. #1
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    Default Inverse of a function help

    I need some help with a certain problem.
    The question is:



    Where I is a certain angle, and n is the number of sides.
    I have to find the number of sides a polygon has by using the given angle (108). (Just have to sub 108 into I)

    I got the answer:

    as the inverse

    However, this equation also results in the correct answer:


    The correct answer is 5/Pentagon.
    Are they both right? Am I wrong?
    Last edited by Sin; 04-04-2013 at 06:45 PM.

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    Correct way to solve: http://puu.sh/2tQch

    yours is wrong
    Last edited by Nebula; 04-04-2013 at 07:05 PM.

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    Solve for n:
    (180 (n-2))/n = i
    Multiply both sides by a polynomial to clear fractions.
    Multiply both sides by n:
    180 (n-2) = i n
    Write the linear polynomial on the left hand side in standard form.
    Expand out terms of the left hand side:
    180 n-360 = i n
    Isolate n to the left hand side.
    Subtract -360+i n from both sides:
    (-i+180) n = 360
    Solve for n.
    Divide both sides by 180-i:
    Answer: |
    | n = (360 i)/32401+64800/32401

    On my phone doing wolfram




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    Working on: Tithe Farmer

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    @masterBB , what software do you use for visulisation or do u use mathML/LaTeX

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    Quote Originally Posted by Enslaved View Post
    @masterBB , what software do you use for visulisation or do u use mathML/LaTeX
    People ask me that a lot. I simply use Microsoft Word.
    Working on: Tithe Farmer

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    Sin, you're making the mistake of thinking you need to form the inverse of the function, which you don't need to do at all. When you inverse a function, it actually become an entirely different thing (it's actually a reflection in y=x).

    What you need to do is simply sub the value of i in:

    108 = 180 - 360/n
    -72 = -360/n (minus 180)
    -72n = -360 (time by n)
    -n = -5 OR n = 5 (divide by 72 [or -72])

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    Damn <.<
    Gg 2marks..

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