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Calculate the limit of the series

  • Thread starter sedaw
  • Start date
  • #1
62
0
need to calculate the limit of the series

(cos(a/n))^(n^3) n goes to infinity and a=!0


i try that :

e^L


L= the limit of (n^3)*ln(cos(a/n))


what now ???


TNX !
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
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L has the form 0*infinity. Use l'Hopital's theorem on it to try and figure out the limit. You may have to use l'Hopital more than once.
 
  • #3
62
0


L has the form 0*infinity. Use l'Hopital's theorem on it to try and figure out the limit. You may have to use l'Hopital more than once.
hello Dick !

first of all tnx.

i cant use l'Hopital's theorem cause n =1,2,3.....

so F(n) not differentiable .
 
  • #4
Dick
Science Advisor
Homework Helper
26,258
618


f(x)=ln(cos(a/x))*x^3 is differentiable. If you know the limit of f(x) as x->infinity, then you know the limit of L as n->infinity.
 

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