Sunday, 10 May 2015

calculus - The limit of fn=fracexsin(x)sin(2x)cdotssin(nx)sqrtn




I want to calculate a limit of fn=exsin(x)sin(2x)sin(nx)n if n goes to an infinity.




I was wondering if I can use this: limnsin(nx)n=0, because I have doubts.



I know that limxx0f(x)g(x)=limxx0g(x)limxx0f(x)

(or I suppose), but what if the limit of f(x) or g(x) is zero



My attempt of a solution:



limnexsin(x)sin(2x)...sin(nx)n=limnnexsin(x)sin(2x)...sin(nx)n=limnnexsin(x)sin(2x)sin(nx)n=limnnexsin(x)sin(2x)0=0



And the range for the convergence is , right?


Answer



Hint: sin(x) is always between 1 and 0. But the denominator keeps getting larger as n goes to infinity.


No comments:

Post a Comment

real analysis - How to find limhrightarrow0fracsin(ha)h

How to find limh0sin(ha)h without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...