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prove-that-0-1-1-1-t-n-t-dt-k-1-n-1-k-




Question Number 40889 by abdo.msup.com last updated on 28/Jul/18
prove?that  ∫_0 ^1   ((1−(1−t)^n )/t)dt =Σ_(k=1) ^n  (1/k)
prove?that011(1t)ntdt=k=1n1k
Answered by math khazana by abdo last updated on 30/Jul/18
we have 1−x^n =(1−x)(1+x+x^2  +...+x^(n−1) )⇒  ((1−(1−t)^n )/t) =((t(1+(1−t)+(1−t)^2 +...+(1−t)^(n−1) )/t)  ∫_0 ^1   ((1−(1−t))/t)dt =∫_0 ^1  Σ_(k=0) ^(n−1) (1−t)^k dt  =Σ_(k=0) ^(n−1)  ∫_0 ^1 (1−t)^k dt =Σ_(k=0) ^n [−(1/(k+1))(1−t)^(k+1) ]_0 ^1   =Σ_(k=0) ^(n−1)   (1/(k+1)) =Σ_(k=1) ^n  (1/k)  (=H_n ).
wehave1xn=(1x)(1+x+x2++xn1)1(1t)nt=t(1+(1t)+(1t)2++(1t)n1t011(1t)tdt=01k=0n1(1t)kdt=k=0n101(1t)kdt=k=0n[1k+1(1t)k+1]01=k=0n11k+1=k=1n1k(=Hn).

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