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)?










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$endgroup$








  • 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






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share|cite|improve this question













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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









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    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






























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