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let-f-n-x-1-1-x-n-1-1-n-defined-on-0-1-1-prove-that-f-n-cs-to-a-function-f-on-0-1-2-calculate-I-n-0-1-f-n-x-dx-




Question Number 66344 by mathmax by abdo last updated on 12/Aug/19
let f_n (x)=(1/((1+x^n )^(1+(1/n)) ))   defined on [0,1]  1)prove that f_n →^(cs)   to a function f on[0,1]  2) calculate I_n =∫_0 ^1 f_n (x)dx
letfn(x)=1(1+xn)1+1ndefinedon[0,1]1)provethatfncstoafunctionfon[0,1]2)calculateIn=01fn(x)dx
Commented by mathmax by abdo last updated on 19/Aug/19
1) ona f_n (0) =1 and f_n (1) =(1/2^(1+(1/n)) ) →(1/2) (n→+∞) and for 0<x<1  f_n (x) =(1+x^n )^(−(1+(1/n)))  =e^(−(1+(1/n))ln(1+x^n ))    we have x^n  →0 ⇒  ln(1+x^n )∼x^n  ⇒−(1+(1/n))ln(1+x^n )∼−(1+(1/n))x^n  ⇒  f_n (x)∼e^(−(1+(1/n))x^(n ) )  ⇒  f_n ^(     cs) → 1   on]0,1[
1)onafn(0)=1andfn(1)=121+1n12(n+)andfor0<x<1fn(x)=(1+xn)(1+1n)=e(1+1n)ln(1+xn)wehavexn0ln(1+xn)xn(1+1n)ln(1+xn)(1+1n)xnfn(x)e(1+1n)xnfncs1on]0,1[

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