Limits of sin(x)sin(1/x) when x approaches 0

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I came across this problem as shown in the title.
Limit of sin(x)sin(1/x) as x approaches 0. I plot the graph using online graphing calculators and found that it is approaching zero. But can anybody please proof it? I am really stuck and don't know where to start.



Also I did try to search the internet and found that the limit of xsin(1/x) equals to zero as x approaches zero. I understand how that work. So my second question is can I say that limit of
sin(x)sin(1/x) is the same as limit xsin(1/x) when x approaches zero, since limit of sin(x)/x equals 1 when x approaches zero?










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  • 5




    Observe that $|sin(1/x)| leq 1$, so $|sin(x)sin(1/x)| leq |sin(x)|$.
    – Bungo
    Sep 4 at 7:16










  • thanks a lot everyone
    – JoisBack
    Sep 4 at 7:25














up vote
0
down vote

favorite












I came across this problem as shown in the title.
Limit of sin(x)sin(1/x) as x approaches 0. I plot the graph using online graphing calculators and found that it is approaching zero. But can anybody please proof it? I am really stuck and don't know where to start.



Also I did try to search the internet and found that the limit of xsin(1/x) equals to zero as x approaches zero. I understand how that work. So my second question is can I say that limit of
sin(x)sin(1/x) is the same as limit xsin(1/x) when x approaches zero, since limit of sin(x)/x equals 1 when x approaches zero?










share|cite|improve this question

















  • 5




    Observe that $|sin(1/x)| leq 1$, so $|sin(x)sin(1/x)| leq |sin(x)|$.
    – Bungo
    Sep 4 at 7:16










  • thanks a lot everyone
    – JoisBack
    Sep 4 at 7:25












up vote
0
down vote

favorite









up vote
0
down vote

favorite











I came across this problem as shown in the title.
Limit of sin(x)sin(1/x) as x approaches 0. I plot the graph using online graphing calculators and found that it is approaching zero. But can anybody please proof it? I am really stuck and don't know where to start.



Also I did try to search the internet and found that the limit of xsin(1/x) equals to zero as x approaches zero. I understand how that work. So my second question is can I say that limit of
sin(x)sin(1/x) is the same as limit xsin(1/x) when x approaches zero, since limit of sin(x)/x equals 1 when x approaches zero?










share|cite|improve this question













I came across this problem as shown in the title.
Limit of sin(x)sin(1/x) as x approaches 0. I plot the graph using online graphing calculators and found that it is approaching zero. But can anybody please proof it? I am really stuck and don't know where to start.



Also I did try to search the internet and found that the limit of xsin(1/x) equals to zero as x approaches zero. I understand how that work. So my second question is can I say that limit of
sin(x)sin(1/x) is the same as limit xsin(1/x) when x approaches zero, since limit of sin(x)/x equals 1 when x approaches zero?







limits






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asked Sep 4 at 7:14









JoisBack

1355




1355







  • 5




    Observe that $|sin(1/x)| leq 1$, so $|sin(x)sin(1/x)| leq |sin(x)|$.
    – Bungo
    Sep 4 at 7:16










  • thanks a lot everyone
    – JoisBack
    Sep 4 at 7:25












  • 5




    Observe that $|sin(1/x)| leq 1$, so $|sin(x)sin(1/x)| leq |sin(x)|$.
    – Bungo
    Sep 4 at 7:16










  • thanks a lot everyone
    – JoisBack
    Sep 4 at 7:25







5




5




Observe that $|sin(1/x)| leq 1$, so $|sin(x)sin(1/x)| leq |sin(x)|$.
– Bungo
Sep 4 at 7:16




Observe that $|sin(1/x)| leq 1$, so $|sin(x)sin(1/x)| leq |sin(x)|$.
– Bungo
Sep 4 at 7:16












thanks a lot everyone
– JoisBack
Sep 4 at 7:25




thanks a lot everyone
– JoisBack
Sep 4 at 7:25










2 Answers
2






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up vote
3
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HINT



Let observe that since $forall theta: , |sin theta|le 1$



$$0le |sin x cdot sin(1/x)|=|sin x| cdot |sin(1/x)|le |sin x|$$



then refer to squeeze theorem.




Note that the result you are referring to, that is



$$xcdot sinleft(frac1xright)to 0$$



can be obtained in the same way by squeeze theorem



$$0le |x cdot sin(1/x)|=|x| cdot |sin(1/x)|le |x|to 0$$



once we know that, we can also proceed by standards limit and conclude that



$$sin x cdot sinleft(frac1xright)=fracsin xx cdot x cdot sinleft(frac1xright)to 1 cdot 0 = 0$$



but it is a pretty convolute way since we can apply directly the squeeze theorem to the given limit.






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    up vote
    2
    down vote













    HINT:
    $$
    |sin xsin(1/x)|leq|x|cdot|sin(1/x)|
    $$






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      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes








      up vote
      3
      down vote













      HINT



      Let observe that since $forall theta: , |sin theta|le 1$



      $$0le |sin x cdot sin(1/x)|=|sin x| cdot |sin(1/x)|le |sin x|$$



      then refer to squeeze theorem.




      Note that the result you are referring to, that is



      $$xcdot sinleft(frac1xright)to 0$$



      can be obtained in the same way by squeeze theorem



      $$0le |x cdot sin(1/x)|=|x| cdot |sin(1/x)|le |x|to 0$$



      once we know that, we can also proceed by standards limit and conclude that



      $$sin x cdot sinleft(frac1xright)=fracsin xx cdot x cdot sinleft(frac1xright)to 1 cdot 0 = 0$$



      but it is a pretty convolute way since we can apply directly the squeeze theorem to the given limit.






      share|cite|improve this answer


























        up vote
        3
        down vote













        HINT



        Let observe that since $forall theta: , |sin theta|le 1$



        $$0le |sin x cdot sin(1/x)|=|sin x| cdot |sin(1/x)|le |sin x|$$



        then refer to squeeze theorem.




        Note that the result you are referring to, that is



        $$xcdot sinleft(frac1xright)to 0$$



        can be obtained in the same way by squeeze theorem



        $$0le |x cdot sin(1/x)|=|x| cdot |sin(1/x)|le |x|to 0$$



        once we know that, we can also proceed by standards limit and conclude that



        $$sin x cdot sinleft(frac1xright)=fracsin xx cdot x cdot sinleft(frac1xright)to 1 cdot 0 = 0$$



        but it is a pretty convolute way since we can apply directly the squeeze theorem to the given limit.






        share|cite|improve this answer
























          up vote
          3
          down vote










          up vote
          3
          down vote









          HINT



          Let observe that since $forall theta: , |sin theta|le 1$



          $$0le |sin x cdot sin(1/x)|=|sin x| cdot |sin(1/x)|le |sin x|$$



          then refer to squeeze theorem.




          Note that the result you are referring to, that is



          $$xcdot sinleft(frac1xright)to 0$$



          can be obtained in the same way by squeeze theorem



          $$0le |x cdot sin(1/x)|=|x| cdot |sin(1/x)|le |x|to 0$$



          once we know that, we can also proceed by standards limit and conclude that



          $$sin x cdot sinleft(frac1xright)=fracsin xx cdot x cdot sinleft(frac1xright)to 1 cdot 0 = 0$$



          but it is a pretty convolute way since we can apply directly the squeeze theorem to the given limit.






          share|cite|improve this answer














          HINT



          Let observe that since $forall theta: , |sin theta|le 1$



          $$0le |sin x cdot sin(1/x)|=|sin x| cdot |sin(1/x)|le |sin x|$$



          then refer to squeeze theorem.




          Note that the result you are referring to, that is



          $$xcdot sinleft(frac1xright)to 0$$



          can be obtained in the same way by squeeze theorem



          $$0le |x cdot sin(1/x)|=|x| cdot |sin(1/x)|le |x|to 0$$



          once we know that, we can also proceed by standards limit and conclude that



          $$sin x cdot sinleft(frac1xright)=fracsin xx cdot x cdot sinleft(frac1xright)to 1 cdot 0 = 0$$



          but it is a pretty convolute way since we can apply directly the squeeze theorem to the given limit.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Sep 4 at 8:39

























          answered Sep 4 at 7:17









          gimusi

          72.8k73889




          72.8k73889




















              up vote
              2
              down vote













              HINT:
              $$
              |sin xsin(1/x)|leq|x|cdot|sin(1/x)|
              $$






              share|cite|improve this answer
























                up vote
                2
                down vote













                HINT:
                $$
                |sin xsin(1/x)|leq|x|cdot|sin(1/x)|
                $$






                share|cite|improve this answer






















                  up vote
                  2
                  down vote










                  up vote
                  2
                  down vote









                  HINT:
                  $$
                  |sin xsin(1/x)|leq|x|cdot|sin(1/x)|
                  $$






                  share|cite|improve this answer












                  HINT:
                  $$
                  |sin xsin(1/x)|leq|x|cdot|sin(1/x)|
                  $$







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Sep 4 at 7:17









                  Przemysław Scherwentke

                  11.8k52751




                  11.8k52751



























                       

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