Finding limit of $sin(x^2/2)/sqrt{2}sin^2(x/2)$ as $xrightarrow0$
$begingroup$
Can anybody help me find the limit as $x$ tends to $0$, for $$frac{sin(x^2/2)}{sqrt{2}sin^2(x/2)}.$$ How can I simplify the expression or use equivalent transformations to find a limit (without using L'Hospital)?
limits functions limits-without-lhopital
$endgroup$
add a comment |
$begingroup$
Can anybody help me find the limit as $x$ tends to $0$, for $$frac{sin(x^2/2)}{sqrt{2}sin^2(x/2)}.$$ How can I simplify the expression or use equivalent transformations to find a limit (without using L'Hospital)?
limits functions limits-without-lhopital
$endgroup$
2
$begingroup$
Please refer to this guide on how to typeset maths on this site. It's pretty hard to understand what is your expression you are working with
$endgroup$
– roman
Jan 22 at 15:21
$begingroup$
Use Taylor expansions.
$endgroup$
– Clayton
Jan 22 at 15:23
4
$begingroup$
HINT: Note that $$frac{sin(x^2/2)}{sqrt2 sin^2(x/2)}=left(frac{sin(x^2/2)}{x^2/2}right)left(frac{x^2}{2}right)frac{1}{sqrt2}left(frac{x/2}{sin(x/2)}right)^2left(frac{1}{(x/2)^2}right)$$Can you finish now?
$endgroup$
– Mark Viola
Jan 22 at 15:24
add a comment |
$begingroup$
Can anybody help me find the limit as $x$ tends to $0$, for $$frac{sin(x^2/2)}{sqrt{2}sin^2(x/2)}.$$ How can I simplify the expression or use equivalent transformations to find a limit (without using L'Hospital)?
limits functions limits-without-lhopital
$endgroup$
Can anybody help me find the limit as $x$ tends to $0$, for $$frac{sin(x^2/2)}{sqrt{2}sin^2(x/2)}.$$ How can I simplify the expression or use equivalent transformations to find a limit (without using L'Hospital)?
limits functions limits-without-lhopital
limits functions limits-without-lhopital
edited Jan 23 at 1:57
Alexander Gruber♦
20.2k25102173
20.2k25102173
asked Jan 22 at 15:16
Ieva BrakmaneIeva Brakmane
163
163
2
$begingroup$
Please refer to this guide on how to typeset maths on this site. It's pretty hard to understand what is your expression you are working with
$endgroup$
– roman
Jan 22 at 15:21
$begingroup$
Use Taylor expansions.
$endgroup$
– Clayton
Jan 22 at 15:23
4
$begingroup$
HINT: Note that $$frac{sin(x^2/2)}{sqrt2 sin^2(x/2)}=left(frac{sin(x^2/2)}{x^2/2}right)left(frac{x^2}{2}right)frac{1}{sqrt2}left(frac{x/2}{sin(x/2)}right)^2left(frac{1}{(x/2)^2}right)$$Can you finish now?
$endgroup$
– Mark Viola
Jan 22 at 15:24
add a comment |
2
$begingroup$
Please refer to this guide on how to typeset maths on this site. It's pretty hard to understand what is your expression you are working with
$endgroup$
– roman
Jan 22 at 15:21
$begingroup$
Use Taylor expansions.
$endgroup$
– Clayton
Jan 22 at 15:23
4
$begingroup$
HINT: Note that $$frac{sin(x^2/2)}{sqrt2 sin^2(x/2)}=left(frac{sin(x^2/2)}{x^2/2}right)left(frac{x^2}{2}right)frac{1}{sqrt2}left(frac{x/2}{sin(x/2)}right)^2left(frac{1}{(x/2)^2}right)$$Can you finish now?
$endgroup$
– Mark Viola
Jan 22 at 15:24
2
2
$begingroup$
Please refer to this guide on how to typeset maths on this site. It's pretty hard to understand what is your expression you are working with
$endgroup$
– roman
Jan 22 at 15:21
$begingroup$
Please refer to this guide on how to typeset maths on this site. It's pretty hard to understand what is your expression you are working with
$endgroup$
– roman
Jan 22 at 15:21
$begingroup$
Use Taylor expansions.
$endgroup$
– Clayton
Jan 22 at 15:23
$begingroup$
Use Taylor expansions.
$endgroup$
– Clayton
Jan 22 at 15:23
4
4
$begingroup$
HINT: Note that $$frac{sin(x^2/2)}{sqrt2 sin^2(x/2)}=left(frac{sin(x^2/2)}{x^2/2}right)left(frac{x^2}{2}right)frac{1}{sqrt2}left(frac{x/2}{sin(x/2)}right)^2left(frac{1}{(x/2)^2}right)$$Can you finish now?
$endgroup$
– Mark Viola
Jan 22 at 15:24
$begingroup$
HINT: Note that $$frac{sin(x^2/2)}{sqrt2 sin^2(x/2)}=left(frac{sin(x^2/2)}{x^2/2}right)left(frac{x^2}{2}right)frac{1}{sqrt2}left(frac{x/2}{sin(x/2)}right)^2left(frac{1}{(x/2)^2}right)$$Can you finish now?
$endgroup$
– Mark Viola
Jan 22 at 15:24
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
I will be using just one fact to solve this, and that is,
$$lim_{xto 0} frac{ sin x}{x} = 1$$
So lets start!
$$lim_{xto 0} frac {sin frac {x^2}{2}}{sqrt{2} ; sin^2 frac {x}{2}}$$
Now, Multiply and divide by, $frac{x^2}{2} ;$ and $(frac {x}{2})^2$
The $frac{x^2}{2}$ term in the denominator along with $sin frac {x^2}{2}$ in the numerator tends to ONE. And so is the case with the $(frac {x}{2})^2$ in the numerator and $sin^2 frac {x}{2}$ in the denominator.
After that we see that the remaining $x^2$ terms cancel out (because we have one both in the numerator and the denominator).
Resulting in the answer (cue the drumroll) $$sqrt 2$$
Edit: I have included the steps taken just as a measure
$endgroup$
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
|
show 1 more comment
$begingroup$
As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.
Hence
$$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
=lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$
$endgroup$
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%2f3083288%2ffinding-limit-of-sinx2-2-sqrt2-sin2x-2-as-x-rightarrow0%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
I will be using just one fact to solve this, and that is,
$$lim_{xto 0} frac{ sin x}{x} = 1$$
So lets start!
$$lim_{xto 0} frac {sin frac {x^2}{2}}{sqrt{2} ; sin^2 frac {x}{2}}$$
Now, Multiply and divide by, $frac{x^2}{2} ;$ and $(frac {x}{2})^2$
The $frac{x^2}{2}$ term in the denominator along with $sin frac {x^2}{2}$ in the numerator tends to ONE. And so is the case with the $(frac {x}{2})^2$ in the numerator and $sin^2 frac {x}{2}$ in the denominator.
After that we see that the remaining $x^2$ terms cancel out (because we have one both in the numerator and the denominator).
Resulting in the answer (cue the drumroll) $$sqrt 2$$
Edit: I have included the steps taken just as a measure
$endgroup$
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
|
show 1 more comment
$begingroup$
I will be using just one fact to solve this, and that is,
$$lim_{xto 0} frac{ sin x}{x} = 1$$
So lets start!
$$lim_{xto 0} frac {sin frac {x^2}{2}}{sqrt{2} ; sin^2 frac {x}{2}}$$
Now, Multiply and divide by, $frac{x^2}{2} ;$ and $(frac {x}{2})^2$
The $frac{x^2}{2}$ term in the denominator along with $sin frac {x^2}{2}$ in the numerator tends to ONE. And so is the case with the $(frac {x}{2})^2$ in the numerator and $sin^2 frac {x}{2}$ in the denominator.
After that we see that the remaining $x^2$ terms cancel out (because we have one both in the numerator and the denominator).
Resulting in the answer (cue the drumroll) $$sqrt 2$$
Edit: I have included the steps taken just as a measure
$endgroup$
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
|
show 1 more comment
$begingroup$
I will be using just one fact to solve this, and that is,
$$lim_{xto 0} frac{ sin x}{x} = 1$$
So lets start!
$$lim_{xto 0} frac {sin frac {x^2}{2}}{sqrt{2} ; sin^2 frac {x}{2}}$$
Now, Multiply and divide by, $frac{x^2}{2} ;$ and $(frac {x}{2})^2$
The $frac{x^2}{2}$ term in the denominator along with $sin frac {x^2}{2}$ in the numerator tends to ONE. And so is the case with the $(frac {x}{2})^2$ in the numerator and $sin^2 frac {x}{2}$ in the denominator.
After that we see that the remaining $x^2$ terms cancel out (because we have one both in the numerator and the denominator).
Resulting in the answer (cue the drumroll) $$sqrt 2$$
Edit: I have included the steps taken just as a measure
$endgroup$
I will be using just one fact to solve this, and that is,
$$lim_{xto 0} frac{ sin x}{x} = 1$$
So lets start!
$$lim_{xto 0} frac {sin frac {x^2}{2}}{sqrt{2} ; sin^2 frac {x}{2}}$$
Now, Multiply and divide by, $frac{x^2}{2} ;$ and $(frac {x}{2})^2$
The $frac{x^2}{2}$ term in the denominator along with $sin frac {x^2}{2}$ in the numerator tends to ONE. And so is the case with the $(frac {x}{2})^2$ in the numerator and $sin^2 frac {x}{2}$ in the denominator.
After that we see that the remaining $x^2$ terms cancel out (because we have one both in the numerator and the denominator).
Resulting in the answer (cue the drumroll) $$sqrt 2$$
Edit: I have included the steps taken just as a measure
edited Jan 22 at 18:27
answered Jan 22 at 15:46
The Jade EmperorThe Jade Emperor
908
908
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
|
show 1 more comment
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
The $sqrt 2$ which is in the denominator stays out of our calculation. After simplifying we get $$lim_{x to 0} frac{sin frac {x^2}{2}}{sin^2 frac{x}{2}} = 2$$.. and that $2$ cancels with $sqrt 2 $ to give the stated answer
$endgroup$
– The Jade Emperor
Jan 22 at 18:15
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. I will attach all detailed steps
$endgroup$
– The Jade Emperor
Jan 22 at 18:16
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
Ok. Thank you very much.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:25
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
yeah I've edited my answer to show the method. Hope you like it! If you still have questions feel free to ask! ((Otherwise upvote and accept the answer :p))
$endgroup$
– The Jade Emperor
Jan 22 at 18:28
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
$begingroup$
Thank you very much. Maybe you know any good source when one can get accustomized with these set of problems? I accepted the answer, but cannot upvote you as I don't have enough reputation points yet.
$endgroup$
– Ieva Brakmane
Jan 22 at 18:41
|
show 1 more comment
$begingroup$
As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.
Hence
$$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
=lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$
$endgroup$
add a comment |
$begingroup$
As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.
Hence
$$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
=lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$
$endgroup$
add a comment |
$begingroup$
As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.
Hence
$$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
=lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$
$endgroup$
As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.
Hence
$$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
=lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$
answered Jan 22 at 18:48
Yves DaoustYves Daoust
130k676227
130k676227
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%2f3083288%2ffinding-limit-of-sinx2-2-sqrt2-sin2x-2-as-x-rightarrow0%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
2
$begingroup$
Please refer to this guide on how to typeset maths on this site. It's pretty hard to understand what is your expression you are working with
$endgroup$
– roman
Jan 22 at 15:21
$begingroup$
Use Taylor expansions.
$endgroup$
– Clayton
Jan 22 at 15:23
4
$begingroup$
HINT: Note that $$frac{sin(x^2/2)}{sqrt2 sin^2(x/2)}=left(frac{sin(x^2/2)}{x^2/2}right)left(frac{x^2}{2}right)frac{1}{sqrt2}left(frac{x/2}{sin(x/2)}right)^2left(frac{1}{(x/2)^2}right)$$Can you finish now?
$endgroup$
– Mark Viola
Jan 22 at 15:24