Proof of $frac{q_n}{q_{n-1}} = [a_n,a_{n-1},a_{n-2},…,a_2,a_1]$?
$begingroup$
Proof of continued fractions axiom.
Let $c=[a_0,a_1,a_2,dots,a_n,dots] = a_0 + cfrac{1}{a_1 + cfrac{1}{a_2 + ddots}}$ be a continued fraction which could be finite or infinite.
By $frac{p_n}{q_n}$ we denote the $n$-th convergent of the continued fraction, i.e.
$$frac{p_n}{q_n}=[a_0,a_1,a_2,dots,a_n].$$
How to prove the formula formula: $$frac{q_n}{q_{n-1}} = [a_n,a_{n-1},a_{n-2},...,a_2,a_1]?$$
This formula is stated in the book Olds C.D. Continued fractions (Math.Assoc.Am., Yale, 1963) as a part of Problem 7 on page 26, together with a related formula
$$frac{p_n}{p_{n-1}} = [a_n,a_{n-1},dots,a_1,a_0].$$
It is also stated as formula (31) in Wolfram Mathworld article on continued fractions.
visual formula - https://s31.postimg.org/6l4ehkd8r/pic.png
fractions continued-fractions
$endgroup$
add a comment |
$begingroup$
Proof of continued fractions axiom.
Let $c=[a_0,a_1,a_2,dots,a_n,dots] = a_0 + cfrac{1}{a_1 + cfrac{1}{a_2 + ddots}}$ be a continued fraction which could be finite or infinite.
By $frac{p_n}{q_n}$ we denote the $n$-th convergent of the continued fraction, i.e.
$$frac{p_n}{q_n}=[a_0,a_1,a_2,dots,a_n].$$
How to prove the formula formula: $$frac{q_n}{q_{n-1}} = [a_n,a_{n-1},a_{n-2},...,a_2,a_1]?$$
This formula is stated in the book Olds C.D. Continued fractions (Math.Assoc.Am., Yale, 1963) as a part of Problem 7 on page 26, together with a related formula
$$frac{p_n}{p_{n-1}} = [a_n,a_{n-1},dots,a_1,a_0].$$
It is also stated as formula (31) in Wolfram Mathworld article on continued fractions.
visual formula - https://s31.postimg.org/6l4ehkd8r/pic.png
fractions continued-fractions
$endgroup$
1
$begingroup$
I have tried to edit the post. Together with the OPs edits, I do not think the close reason "unclear what you're asking" applies any longer.
$endgroup$
– Martin Sleziak
Jun 19 '16 at 14:45
add a comment |
$begingroup$
Proof of continued fractions axiom.
Let $c=[a_0,a_1,a_2,dots,a_n,dots] = a_0 + cfrac{1}{a_1 + cfrac{1}{a_2 + ddots}}$ be a continued fraction which could be finite or infinite.
By $frac{p_n}{q_n}$ we denote the $n$-th convergent of the continued fraction, i.e.
$$frac{p_n}{q_n}=[a_0,a_1,a_2,dots,a_n].$$
How to prove the formula formula: $$frac{q_n}{q_{n-1}} = [a_n,a_{n-1},a_{n-2},...,a_2,a_1]?$$
This formula is stated in the book Olds C.D. Continued fractions (Math.Assoc.Am., Yale, 1963) as a part of Problem 7 on page 26, together with a related formula
$$frac{p_n}{p_{n-1}} = [a_n,a_{n-1},dots,a_1,a_0].$$
It is also stated as formula (31) in Wolfram Mathworld article on continued fractions.
visual formula - https://s31.postimg.org/6l4ehkd8r/pic.png
fractions continued-fractions
$endgroup$
Proof of continued fractions axiom.
Let $c=[a_0,a_1,a_2,dots,a_n,dots] = a_0 + cfrac{1}{a_1 + cfrac{1}{a_2 + ddots}}$ be a continued fraction which could be finite or infinite.
By $frac{p_n}{q_n}$ we denote the $n$-th convergent of the continued fraction, i.e.
$$frac{p_n}{q_n}=[a_0,a_1,a_2,dots,a_n].$$
How to prove the formula formula: $$frac{q_n}{q_{n-1}} = [a_n,a_{n-1},a_{n-2},...,a_2,a_1]?$$
This formula is stated in the book Olds C.D. Continued fractions (Math.Assoc.Am., Yale, 1963) as a part of Problem 7 on page 26, together with a related formula
$$frac{p_n}{p_{n-1}} = [a_n,a_{n-1},dots,a_1,a_0].$$
It is also stated as formula (31) in Wolfram Mathworld article on continued fractions.
visual formula - https://s31.postimg.org/6l4ehkd8r/pic.png
fractions continued-fractions
fractions continued-fractions
edited Jun 19 '16 at 14:39
Martin Sleziak
44.8k9118272
44.8k9118272
asked Jun 18 '16 at 16:22
qwerryqwerry
314
314
1
$begingroup$
I have tried to edit the post. Together with the OPs edits, I do not think the close reason "unclear what you're asking" applies any longer.
$endgroup$
– Martin Sleziak
Jun 19 '16 at 14:45
add a comment |
1
$begingroup$
I have tried to edit the post. Together with the OPs edits, I do not think the close reason "unclear what you're asking" applies any longer.
$endgroup$
– Martin Sleziak
Jun 19 '16 at 14:45
1
1
$begingroup$
I have tried to edit the post. Together with the OPs edits, I do not think the close reason "unclear what you're asking" applies any longer.
$endgroup$
– Martin Sleziak
Jun 19 '16 at 14:45
$begingroup$
I have tried to edit the post. Together with the OPs edits, I do not think the close reason "unclear what you're asking" applies any longer.
$endgroup$
– Martin Sleziak
Jun 19 '16 at 14:45
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
Ok, I guess it is by far simple answer, sorry for posting silly questions :(.
$frac{q_n}{q_{n-1}}$ =
$frac{a_n*q_{n-1}+q_{n-2}}{q_{n-1}}$ =
$frac{a_n*q_{n-1}}{q_{n-1}}$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
So $frac{q_n}{q_{n-1}}$ = $a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
and $frac{q_{n-1}}{q_{n-2}}$ = $a_{n-1}$ + $frac{1}{frac{q_{n-2}}{q_{n-3}}}$
and $frac{q_{n-2}}{q_{n-3}}$ = $a_{n-2}$ + $frac{1}{frac{q_{n-3}}{q_{n-4}}}$
$vdots$
So by induction you will have:
$frac{q_n}{q_{n-1}}$ =
$a_n$ + $frac{1}
{a_{n-1} + frac{1}
{a_{n-2} + frac{1}
{frac{q_{n-3}}{
ddots}}}}$ = $[a_{n},a_{n-1},a_{n-2},dots,a_{1}]$
$endgroup$
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f1831001%2fproof-of-fracq-nq-n-1-a-n-a-n-1-a-n-2-a-2-a-1%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Ok, I guess it is by far simple answer, sorry for posting silly questions :(.
$frac{q_n}{q_{n-1}}$ =
$frac{a_n*q_{n-1}+q_{n-2}}{q_{n-1}}$ =
$frac{a_n*q_{n-1}}{q_{n-1}}$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
So $frac{q_n}{q_{n-1}}$ = $a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
and $frac{q_{n-1}}{q_{n-2}}$ = $a_{n-1}$ + $frac{1}{frac{q_{n-2}}{q_{n-3}}}$
and $frac{q_{n-2}}{q_{n-3}}$ = $a_{n-2}$ + $frac{1}{frac{q_{n-3}}{q_{n-4}}}$
$vdots$
So by induction you will have:
$frac{q_n}{q_{n-1}}$ =
$a_n$ + $frac{1}
{a_{n-1} + frac{1}
{a_{n-2} + frac{1}
{frac{q_{n-3}}{
ddots}}}}$ = $[a_{n},a_{n-1},a_{n-2},dots,a_{1}]$
$endgroup$
add a comment |
$begingroup$
Ok, I guess it is by far simple answer, sorry for posting silly questions :(.
$frac{q_n}{q_{n-1}}$ =
$frac{a_n*q_{n-1}+q_{n-2}}{q_{n-1}}$ =
$frac{a_n*q_{n-1}}{q_{n-1}}$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
So $frac{q_n}{q_{n-1}}$ = $a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
and $frac{q_{n-1}}{q_{n-2}}$ = $a_{n-1}$ + $frac{1}{frac{q_{n-2}}{q_{n-3}}}$
and $frac{q_{n-2}}{q_{n-3}}$ = $a_{n-2}$ + $frac{1}{frac{q_{n-3}}{q_{n-4}}}$
$vdots$
So by induction you will have:
$frac{q_n}{q_{n-1}}$ =
$a_n$ + $frac{1}
{a_{n-1} + frac{1}
{a_{n-2} + frac{1}
{frac{q_{n-3}}{
ddots}}}}$ = $[a_{n},a_{n-1},a_{n-2},dots,a_{1}]$
$endgroup$
add a comment |
$begingroup$
Ok, I guess it is by far simple answer, sorry for posting silly questions :(.
$frac{q_n}{q_{n-1}}$ =
$frac{a_n*q_{n-1}+q_{n-2}}{q_{n-1}}$ =
$frac{a_n*q_{n-1}}{q_{n-1}}$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
So $frac{q_n}{q_{n-1}}$ = $a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
and $frac{q_{n-1}}{q_{n-2}}$ = $a_{n-1}$ + $frac{1}{frac{q_{n-2}}{q_{n-3}}}$
and $frac{q_{n-2}}{q_{n-3}}$ = $a_{n-2}$ + $frac{1}{frac{q_{n-3}}{q_{n-4}}}$
$vdots$
So by induction you will have:
$frac{q_n}{q_{n-1}}$ =
$a_n$ + $frac{1}
{a_{n-1} + frac{1}
{a_{n-2} + frac{1}
{frac{q_{n-3}}{
ddots}}}}$ = $[a_{n},a_{n-1},a_{n-2},dots,a_{1}]$
$endgroup$
Ok, I guess it is by far simple answer, sorry for posting silly questions :(.
$frac{q_n}{q_{n-1}}$ =
$frac{a_n*q_{n-1}+q_{n-2}}{q_{n-1}}$ =
$frac{a_n*q_{n-1}}{q_{n-1}}$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ +
$frac{q_{n-2}}{q_{n-1}}$ =
$a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
So $frac{q_n}{q_{n-1}}$ = $a_n$ + $frac{1}{frac{q_{n-1}}{q_{n-2}}}$
and $frac{q_{n-1}}{q_{n-2}}$ = $a_{n-1}$ + $frac{1}{frac{q_{n-2}}{q_{n-3}}}$
and $frac{q_{n-2}}{q_{n-3}}$ = $a_{n-2}$ + $frac{1}{frac{q_{n-3}}{q_{n-4}}}$
$vdots$
So by induction you will have:
$frac{q_n}{q_{n-1}}$ =
$a_n$ + $frac{1}
{a_{n-1} + frac{1}
{a_{n-2} + frac{1}
{frac{q_{n-3}}{
ddots}}}}$ = $[a_{n},a_{n-1},a_{n-2},dots,a_{1}]$
edited Dec 11 '18 at 14:28
Algebear
616319
616319
answered Jun 19 '16 at 21:17
qwerryqwerry
314
314
add a comment |
add a comment |
Thanks for contributing an answer to Mathematics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f1831001%2fproof-of-fracq-nq-n-1-a-n-a-n-1-a-n-2-a-2-a-1%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
1
$begingroup$
I have tried to edit the post. Together with the OPs edits, I do not think the close reason "unclear what you're asking" applies any longer.
$endgroup$
– Martin Sleziak
Jun 19 '16 at 14:45