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Math Help - TI Program

  1. #1
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    TI Program

    This is driving me mad...

    Can anyone tell me how to do the following equation on a calculator?

    1 / [1 + e-(1*0.5+1*0.4-1*0.8)]

    Cheers,
    TK
    Last edited by tomjkear; May 10th 2008 at 05:04 AM. Reason: Missing a bracket
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  2. #2
    Moo
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    Quote Originally Posted by tomjkear View Post
    This is driving me mad...

    Can anyone tell me how to do the following equation on a calculator?

    1 / [1 + e-(1*0.5+1*0.4-1*0.8)

    Cheers,
    TK
    Hello,

    There is no equation in there... oO
    And which calculator ?
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  3. #3
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    Quote Originally Posted by Moo View Post
    Hello,

    There is no equation in there... oO
    And which calculator ?
    That is a sigmoidal function.

    I do not understand the purpose / value of e?
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  4. #4
    Moo
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    Quote Originally Posted by tomjkear View Post
    That is a sigmoidal function.

    I do not understand the purpose / value of e?
    Oh, I see

    e has a value approaching 2.7. Actually it's e^(...).
    It's the exponential function : Exponential function - Wikipedia, the free encyclopedia

    So if you want to enter the function in your calculator, it should be :

    1/(1+e^(-(1*0.5+1*0.4-1*0.8)))
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  5. #5
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    Quote Originally Posted by Moo View Post
    Oh, I see

    e has a value approaching 2.7. Actually it's e^(...).
    It's the exponential function : Exponential function - Wikipedia, the free encyclopedia

    So if you want to enter the function in your calculator, it should be :

    1/(1+e^(-(1*0.5+1*0.4-1*0.8)))
    Thanks.

    I know the result should be 0.5250 according to the textbook I am using. But doing the above in my calculator returns 0.5 for some reason.

    Another similar example that is given is:

    1/(1+e^(-(1*0.9+1*1.0+1*0.1)))

    This should return 0.8808 but also returns 0.5 on my calculator.

    If it helps the calculator is a Sharp EL-530L.
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  6. #6
    Moo
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    Quote Originally Posted by tomjkear View Post
    Thanks.

    I know the result should be 0.5250 according to the textbook I am using. But doing the above in my calculator returns 0.5 for some reason.

    Another similar example that is given is:

    1/(1+e^(-(1*0.9+1*1.0+1*0.1)))

    This should return 0.8808 but also returns 0.5 on my calculator.

    If it helps the calculator is a Sharp EL-530L.
    I don't know this calculator, so I don't know what e represents for them...

    Try typing :

    1/(1+2.71828183^(-(1*0.9+1*1.0+1*0.1)))

    (because e ~ 2,71828183)
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  7. #7
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    Quote Originally Posted by Moo View Post
    I don't know this calculator, so I don't know what e represents for them...

    Try typing :

    1/(1+2.71828183^(-(1*0.9+1*1.0+1*0.1)))

    (because e ~ 2,71828183)
    Thanks for the help.
    I have tried a diffferent calculator and it returns the correct results.
    Not sure what is the matter with mine but I will get a replacement for the exam
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