Finding limit of $sin(x^2/2)/sqrt{2}sin^2(x/2)$ as $xrightarrow0$












1












$begingroup$


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)?










share|cite|improve this question











$endgroup$








  • 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


















1












$begingroup$


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)?










share|cite|improve this question











$endgroup$








  • 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
















1












1








1





$begingroup$


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)?










share|cite|improve this question











$endgroup$




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






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








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
















  • 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












2 Answers
2






active

oldest

votes


















2












$begingroup$

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 measureenter image description here






share|cite|improve this answer











$endgroup$













  • $begingroup$
    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





















0












$begingroup$

As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.



Hence



$$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
=lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$






share|cite|improve this answer









$endgroup$













    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
    });


    }
    });














    draft saved

    draft discarded


















    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









    2












    $begingroup$

    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 measureenter image description here






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      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


















    2












    $begingroup$

    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 measureenter image description here






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      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
















    2












    2








    2





    $begingroup$

    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 measureenter image description here






    share|cite|improve this answer











    $endgroup$



    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 measureenter image description here







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    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




















    • $begingroup$
      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













    0












    $begingroup$

    As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.



    Hence



    $$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
    =lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.



      Hence



      $$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
      =lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.



        Hence



        $$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
        =lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$






        share|cite|improve this answer









        $endgroup$



        As $dfrac{sin x}x=1$, in multiplicative expressions you can replace $sin x$ by $x$.



        Hence



        $$lim_{xto0}frac{sinleft(dfrac{x^2}2right)}{sqrt2,sin^2left(dfrac x2right)}
        =lim_{xto0}frac{dfrac{x^2}2}{sqrt2,left(dfrac x2right)^2}=sqrt2.$$







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 22 at 18:48









        Yves DaoustYves Daoust

        130k676227




        130k676227






























            draft saved

            draft discarded




















































            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.




            draft saved


            draft discarded














            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





















































            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







            Popular posts from this blog

            Can a sorcerer learn a 5th-level spell early by creating spell slots using the Font of Magic feature?

            ts Property 'filter' does not exist on type '{}'

            mat-slide-toggle shouldn't change it's state when I click cancel in confirmation window