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Question Number 31672 by gunawan last updated on 12/Mar/18
for what value p is a series  Σ_(n=1) ^∞ ((1/n)−sin (1/n))^p   convergens ?
forwhatvaluepisaseriesMissing \left or extra \right
Commented by abdo imad last updated on 12/Mar/18
sinx =x −(x^3 /6) +o(x^5 )  ⇒sin((1/n))=(1/n) −(1/(6n^3 )) +o((1/n^5 ))(n→∞)  ⇒−sin((1/n))=−(1/n) +(1/(6n^3 )) +o((1/n^5 )) ⇒(1/n) −sin((1/n))=(1/(6n^3 )) +o((1/n^5 ))⇒  ((1/n) −sin((1/n)))^p  ∼  (1/(6n^(3p) ))  and the serie Σ_(p≥1)  (1/(6n^(3p) )) converges  if  3p>1 ⇔ p >(1/3)  f p is integr we must have p≥1 .
sinx=xx36+o(x5)sin(1n)=1n16n3+o(1n5)(n)sin(1n)=1n+16n3+o(1n5)1nsin(1n)=16n3+o(1n5)(1nsin(1n))p16n3pandtheseriep116n3pconvergesif3p>1p>13fpisintegrwemusthavep1.
Commented by gunawan last updated on 12/Mar/18
thank you Sir
thankyouSir

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