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Math Help - sequence help

  1. #1
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    sequence help

    Let an be the a_n th digit after the decimal point in
    7 pi+2e . Evaluate
    \sum_{n=1}^\infty a_n (.1)^n.

    can someone show me how to solve this.
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  2. #2
    Super Member Matt Westwood's Avatar
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    Trick question.

    The answer is 7 \pi + 2 e.

    Think about it.
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  3. #3
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    Quote Originally Posted by dat1611 View Post
    Let an be the a_n th digit after the decimal point in
    7 pi+2e . Evaluate
    \sum_{n=1}^\infty a_n (.1)^n.

    can someone show me how to solve this.
    Should be your question like this:
    Let a_n be the n th digit after the decimal point in 7\pi+2e . Evaluate \sum_{n=1}^\infty a_n (.1)^n.

    If so, the result would be 7\pi+2e-\lfloor 7\pi+2e \rfloor

    If not, please clarify.
    Last edited by mr fantastic; September 18th 2009 at 08:59 AM. Reason: Restored orignal reply
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  4. #4
    Super Member Matt Westwood's Avatar
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    Yes I agree - sorry, ignore my first answer, you need to subtract the integer part from it like Luobo has done.

    It's still a trick question!
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  5. #5
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    is not the correct answer though
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  6. #6
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    Quote Originally Posted by dat1611 View Post
    Let an be the a_n th digit after the decimal point in
    7 pi+2e . Evaluate
    \sum_{n=1}^\infty a_n (.1)^n.

    can someone show me how to solve this.
    "Let an be the a_n th digit after the decimal point in 7 pi+2e"

    What do you mean by this? Does this make any sense?

    You need make your problem clear and correct so that others can help you correct. Do not let people GUESS what you mean.
    Last edited by mr fantastic; September 18th 2009 at 08:59 AM. Reason: Restored original reply
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  7. #7
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    Quote Originally Posted by luobo View Post
    "Let a_n be the a_n th digit after the decimal point in 7 pi+2e"

    What do you mean by this? Does this make any sense?

    You need make your problem clear and correct so that others can help you correct. Do not let people GUESS what you mean.
    its supposed to be "Let a_n be the nth digit after the decimal point in 7 pi+2e"
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  8. #8
    Super Member Matt Westwood's Avatar
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    Okay, so what *is* the correct answer?

    7 \pi + 2 e - \lfloor {7 \pi + 2 e}\rfloor looks fine to me.
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  9. #9
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    Quote Originally Posted by Matt Westwood View Post
    Okay, so what *is* the correct answer?

    7 \pi + 2 e - \lfloor {7 \pi + 2 e}\rfloor looks fine to me.
    what do these mean \lfloor     \rfloor
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  10. #10
    Super Member Matt Westwood's Avatar
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