Continued fraction but no recurrence?

Algebra Level 3

1 1 1 5 16 13 81 25 256 41 625 61 1296 85 = A π B \Large \frac { 1 }{ 1-\frac { 1 }{ 5-\frac { 16 }{ 13-\frac { 81 }{ 25-\frac { 256 }{ 41-\frac { 625 }{ 61-\frac { 1296 }{ 85-\cdots } } } } } } } =A\pi^B

where A A and B B are rational numbers. Find B A \dfrac{B}{A} .


The answer is 12.0.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

By using Euler's continued fraction formula , we change the fraction into another form by expanding or reducing fractions and the formula. 1 1 1 5 16 13 81 25 256 41 625 61 1296 85 = 1 1 1 4 5 4 4 9 13 9 9 16 25 16 16 25 41 25 25 36 61 36 36 49 85 49 = 1 + 1 × 1 4 + 1 × 1 4 × 4 9 + 1 × 1 4 × 4 9 × 9 16 + 1 × 1 4 × 4 9 × 9 16 × 16 25 + 1 × 1 4 × 4 9 × 9 16 × 16 25 × 25 36 + 1 × 1 4 × 4 9 × 9 16 × 16 25 × 25 36 × 36 49 + = 1 + 1 2 2 + 1 3 2 + 1 4 2 + 1 5 2 + 1 6 2 + 1 7 2 + = ζ ( 2 ) = π 2 6 \quad\dfrac{1}{1-\dfrac{1}{5-\dfrac{16}{13-\dfrac{81}{25-\dfrac{256}{41-\dfrac{625}{61-\dfrac{1296}{85-\cdots}}}}}}}\\=\dfrac{1}{1-\dfrac{\frac{1}{4}}{\frac{5}{4}-\dfrac{\frac{4}{9}}{\frac{13}{9}-\dfrac{\frac{9}{16}}{\frac{25}{16}-\dfrac{\frac{16}{25}}{\frac{41}{25}-\dfrac{\frac{25}{36}}{\frac{61}{36}-\dfrac{\frac{36}{49}}{\frac{85}{49}-\cdots}}}}}}} \\= 1+1\times\dfrac{1}{4}+1\times\dfrac{1}{4}\times\dfrac{4}{9}+1\times\dfrac{1}{4}\times\dfrac{4}{9}\times\dfrac{9}{16}+1\times\dfrac{1}{4}\times\dfrac{4}{9}\times\dfrac{9}{16}\times\dfrac{16}{25}+1\times\dfrac{1}{4}\times\dfrac{4}{9}\times\dfrac{9}{16}\times\dfrac{16}{25}\times\dfrac{25}{36}+1\times\dfrac{1}{4}\times\dfrac{4}{9}\times\dfrac{9}{16}\times\dfrac{16}{25}\times\dfrac{25}{36}\times\dfrac{36}{49}+\cdots \\= 1+\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+\dfrac{1}{5^2}+\dfrac{1}{6^2}+\dfrac{1}{7^2}+\cdots=\zeta(2)=\dfrac{\pi^2}{6}

Therefore, A = 1 6 , B = 2 , B A = 12 A=\dfrac{1}{6}, B=2, \dfrac{B}{A}=\boxed{12}

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...