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$I_1=int_0^1 frac 1 1+frac 1 sqrt x dx$


How to prove that $lim limits_nrightarrow infty fracF_n+1F_n=fracsqrt5+12$Fibonacci nth termArctangents, Fibonacci numbers, and the golden ratioMean and Variance of Fibonacci NumbersEvaluating: $I_1 = intsin^-1 left(sqrtfracxx+a;right) dx$$ I = int_0^1 ((y')^2-y^2)dx $ and $I_1= int_0^1 (y' + y tan x)^2dx$Closed form of series involving Fibonacci numbersLimit involving fibonacci series with an integralCalculation of integral $int_0^afracsqrt xsqrt x + sqrta-xdx$Powers of the golden ratio













1












$begingroup$


If we let $I_2= int_0^1 frac 1 1+frac 1 1+sqrt x dx$ and so on, we’re tasked with solving $I_n$. We can show that $I_2 = int frac 1+sqrt x 1-sqrt x + 1 = int frac 1+sqrt x 2+sqrt x $
And that $I_3=int frac 2+sqrt x3+2sqrt x$, and that in general, using $F_n$ to denote the nth Fibonacci number,



$$I_n=int^1_0 fracF_n+F_n-1sqrt xF_n+1+F_n sqrt xdx$$
However, at this point I’m uncertain how to proceed; we obviously have some ratio of Fibonacci’s which looks like the golden ratio, but I’m unsure what substitutions to make to have the golden ratio more clearly emerge as a useful quantity.










share|cite|improve this question









$endgroup$







  • 3




    $begingroup$
    With the substitution $y= sqrtx$, you should be able to compute explicitely the integral... no ?
    $endgroup$
    – TheSilverDoe
    Mar 14 at 15:56






  • 1




    $begingroup$
    Golden ratio is not going to appear in person, unless you take the limit at $ntoinfty$.
    $endgroup$
    – Ivan Neretin
    Mar 14 at 15:57















1












$begingroup$


If we let $I_2= int_0^1 frac 1 1+frac 1 1+sqrt x dx$ and so on, we’re tasked with solving $I_n$. We can show that $I_2 = int frac 1+sqrt x 1-sqrt x + 1 = int frac 1+sqrt x 2+sqrt x $
And that $I_3=int frac 2+sqrt x3+2sqrt x$, and that in general, using $F_n$ to denote the nth Fibonacci number,



$$I_n=int^1_0 fracF_n+F_n-1sqrt xF_n+1+F_n sqrt xdx$$
However, at this point I’m uncertain how to proceed; we obviously have some ratio of Fibonacci’s which looks like the golden ratio, but I’m unsure what substitutions to make to have the golden ratio more clearly emerge as a useful quantity.










share|cite|improve this question









$endgroup$







  • 3




    $begingroup$
    With the substitution $y= sqrtx$, you should be able to compute explicitely the integral... no ?
    $endgroup$
    – TheSilverDoe
    Mar 14 at 15:56






  • 1




    $begingroup$
    Golden ratio is not going to appear in person, unless you take the limit at $ntoinfty$.
    $endgroup$
    – Ivan Neretin
    Mar 14 at 15:57













1












1








1





$begingroup$


If we let $I_2= int_0^1 frac 1 1+frac 1 1+sqrt x dx$ and so on, we’re tasked with solving $I_n$. We can show that $I_2 = int frac 1+sqrt x 1-sqrt x + 1 = int frac 1+sqrt x 2+sqrt x $
And that $I_3=int frac 2+sqrt x3+2sqrt x$, and that in general, using $F_n$ to denote the nth Fibonacci number,



$$I_n=int^1_0 fracF_n+F_n-1sqrt xF_n+1+F_n sqrt xdx$$
However, at this point I’m uncertain how to proceed; we obviously have some ratio of Fibonacci’s which looks like the golden ratio, but I’m unsure what substitutions to make to have the golden ratio more clearly emerge as a useful quantity.










share|cite|improve this question









$endgroup$




If we let $I_2= int_0^1 frac 1 1+frac 1 1+sqrt x dx$ and so on, we’re tasked with solving $I_n$. We can show that $I_2 = int frac 1+sqrt x 1-sqrt x + 1 = int frac 1+sqrt x 2+sqrt x $
And that $I_3=int frac 2+sqrt x3+2sqrt x$, and that in general, using $F_n$ to denote the nth Fibonacci number,



$$I_n=int^1_0 fracF_n+F_n-1sqrt xF_n+1+F_n sqrt xdx$$
However, at this point I’m uncertain how to proceed; we obviously have some ratio of Fibonacci’s which looks like the golden ratio, but I’m unsure what substitutions to make to have the golden ratio more clearly emerge as a useful quantity.







calculus integration sequences-and-series fibonacci-numbers






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Mar 14 at 15:53









Thor KamphefnerThor Kamphefner

836




836







  • 3




    $begingroup$
    With the substitution $y= sqrtx$, you should be able to compute explicitely the integral... no ?
    $endgroup$
    – TheSilverDoe
    Mar 14 at 15:56






  • 1




    $begingroup$
    Golden ratio is not going to appear in person, unless you take the limit at $ntoinfty$.
    $endgroup$
    – Ivan Neretin
    Mar 14 at 15:57












  • 3




    $begingroup$
    With the substitution $y= sqrtx$, you should be able to compute explicitely the integral... no ?
    $endgroup$
    – TheSilverDoe
    Mar 14 at 15:56






  • 1




    $begingroup$
    Golden ratio is not going to appear in person, unless you take the limit at $ntoinfty$.
    $endgroup$
    – Ivan Neretin
    Mar 14 at 15:57







3




3




$begingroup$
With the substitution $y= sqrtx$, you should be able to compute explicitely the integral... no ?
$endgroup$
– TheSilverDoe
Mar 14 at 15:56




$begingroup$
With the substitution $y= sqrtx$, you should be able to compute explicitely the integral... no ?
$endgroup$
– TheSilverDoe
Mar 14 at 15:56




1




1




$begingroup$
Golden ratio is not going to appear in person, unless you take the limit at $ntoinfty$.
$endgroup$
– Ivan Neretin
Mar 14 at 15:57




$begingroup$
Golden ratio is not going to appear in person, unless you take the limit at $ntoinfty$.
$endgroup$
– Ivan Neretin
Mar 14 at 15:57










1 Answer
1






active

oldest

votes


















3












$begingroup$

We define $$j=j(a,b)=int_0^1fraca+sqrt xb+sqrt xdx$$
So we see that
$$j^*(a_1,a_2,a_3,a_4)=int_0^1fraca_1+a_2sqrt xa_3+a_4sqrt xdx=fraca_2a_4jleft(fraca_1a_2,fraca_3a_4right)$$
So then we see that
$$beginalign
j&=int_0^1fraca-b+b+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+int_0^1fracb+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+1
endalign$$

Then we set $x=u^2Rightarrow dx=2udu$:
$$beginalign
int_0^1fracdxb+sqrt x&=2int_0^1fracub+udu\
&=2int_0^1frac-b+b+ub+udu\
&=2-2bint_0^1fracdub+udu\
&=2-2bln|u+b|]_0^1\
&=2+2blnleft|fracbb+1right|
endalign$$

So $$j(a,b)=1+2(a-b)left(1+blnleft|fracbb+1right|right)$$
And your integral is given by $$I_n=j^*(F_n,F_n-1,F_n+1,F_n)=fracF_n-1F_njleft(fracF_nF_n-1,fracF_n+1F_nright)$$






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    1 Answer
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    1 Answer
    1






    active

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    active

    oldest

    votes






    active

    oldest

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    3












    $begingroup$

    We define $$j=j(a,b)=int_0^1fraca+sqrt xb+sqrt xdx$$
    So we see that
    $$j^*(a_1,a_2,a_3,a_4)=int_0^1fraca_1+a_2sqrt xa_3+a_4sqrt xdx=fraca_2a_4jleft(fraca_1a_2,fraca_3a_4right)$$
    So then we see that
    $$beginalign
    j&=int_0^1fraca-b+b+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+int_0^1fracb+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+1
    endalign$$

    Then we set $x=u^2Rightarrow dx=2udu$:
    $$beginalign
    int_0^1fracdxb+sqrt x&=2int_0^1fracub+udu\
    &=2int_0^1frac-b+b+ub+udu\
    &=2-2bint_0^1fracdub+udu\
    &=2-2bln|u+b|]_0^1\
    &=2+2blnleft|fracbb+1right|
    endalign$$

    So $$j(a,b)=1+2(a-b)left(1+blnleft|fracbb+1right|right)$$
    And your integral is given by $$I_n=j^*(F_n,F_n-1,F_n+1,F_n)=fracF_n-1F_njleft(fracF_nF_n-1,fracF_n+1F_nright)$$






    share|cite|improve this answer











    $endgroup$

















      3












      $begingroup$

      We define $$j=j(a,b)=int_0^1fraca+sqrt xb+sqrt xdx$$
      So we see that
      $$j^*(a_1,a_2,a_3,a_4)=int_0^1fraca_1+a_2sqrt xa_3+a_4sqrt xdx=fraca_2a_4jleft(fraca_1a_2,fraca_3a_4right)$$
      So then we see that
      $$beginalign
      j&=int_0^1fraca-b+b+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+int_0^1fracb+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+1
      endalign$$

      Then we set $x=u^2Rightarrow dx=2udu$:
      $$beginalign
      int_0^1fracdxb+sqrt x&=2int_0^1fracub+udu\
      &=2int_0^1frac-b+b+ub+udu\
      &=2-2bint_0^1fracdub+udu\
      &=2-2bln|u+b|]_0^1\
      &=2+2blnleft|fracbb+1right|
      endalign$$

      So $$j(a,b)=1+2(a-b)left(1+blnleft|fracbb+1right|right)$$
      And your integral is given by $$I_n=j^*(F_n,F_n-1,F_n+1,F_n)=fracF_n-1F_njleft(fracF_nF_n-1,fracF_n+1F_nright)$$






      share|cite|improve this answer











      $endgroup$















        3












        3








        3





        $begingroup$

        We define $$j=j(a,b)=int_0^1fraca+sqrt xb+sqrt xdx$$
        So we see that
        $$j^*(a_1,a_2,a_3,a_4)=int_0^1fraca_1+a_2sqrt xa_3+a_4sqrt xdx=fraca_2a_4jleft(fraca_1a_2,fraca_3a_4right)$$
        So then we see that
        $$beginalign
        j&=int_0^1fraca-b+b+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+int_0^1fracb+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+1
        endalign$$

        Then we set $x=u^2Rightarrow dx=2udu$:
        $$beginalign
        int_0^1fracdxb+sqrt x&=2int_0^1fracub+udu\
        &=2int_0^1frac-b+b+ub+udu\
        &=2-2bint_0^1fracdub+udu\
        &=2-2bln|u+b|]_0^1\
        &=2+2blnleft|fracbb+1right|
        endalign$$

        So $$j(a,b)=1+2(a-b)left(1+blnleft|fracbb+1right|right)$$
        And your integral is given by $$I_n=j^*(F_n,F_n-1,F_n+1,F_n)=fracF_n-1F_njleft(fracF_nF_n-1,fracF_n+1F_nright)$$






        share|cite|improve this answer











        $endgroup$



        We define $$j=j(a,b)=int_0^1fraca+sqrt xb+sqrt xdx$$
        So we see that
        $$j^*(a_1,a_2,a_3,a_4)=int_0^1fraca_1+a_2sqrt xa_3+a_4sqrt xdx=fraca_2a_4jleft(fraca_1a_2,fraca_3a_4right)$$
        So then we see that
        $$beginalign
        j&=int_0^1fraca-b+b+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+int_0^1fracb+sqrt xb+sqrt xdx\&=(a-b)int_0^1fracdxb+sqrt x+1
        endalign$$

        Then we set $x=u^2Rightarrow dx=2udu$:
        $$beginalign
        int_0^1fracdxb+sqrt x&=2int_0^1fracub+udu\
        &=2int_0^1frac-b+b+ub+udu\
        &=2-2bint_0^1fracdub+udu\
        &=2-2bln|u+b|]_0^1\
        &=2+2blnleft|fracbb+1right|
        endalign$$

        So $$j(a,b)=1+2(a-b)left(1+blnleft|fracbb+1right|right)$$
        And your integral is given by $$I_n=j^*(F_n,F_n-1,F_n+1,F_n)=fracF_n-1F_njleft(fracF_nF_n-1,fracF_n+1F_nright)$$







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Mar 16 at 18:54

























        answered Mar 14 at 18:12









        clathratusclathratus

        5,1651338




        5,1651338



























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