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Question Number 99975 by Dwaipayan Shikari last updated on 24/Jun/20

((1/2))^(((1/3))^((1/4)....∞) ) =?

(12)(13)14....=?

Answered by bachamohamed last updated on 24/Jun/20

solution:   on a  a_n =((1/2))^(((1/3))^(((1/4))^(........((1/(n+1)))) ) ) .  a_1 =((1/2)) .  a_2 =((1/2))^(((1/3))) =e^((1/3)ln(1/2))     a_3 =((1/2))^(((1/3))^(((1/4))) ) =e^((1/4)ln(((1/2))^(((1/3))) )) =e^((1/4)ln(a_2 )) =e^((1/4)ln(e^((1/3)ln((1/2))) )) =e^((2/(4!))ln((1/2)))      a_4 =((1/2))^(((1/3))^(((1/4))^(((1/5))) ) ) =e^((1/5)ln(((1/2))^(((1/3))^(((1/4))) ) )) =e^((1/5)ln(a_3 )) =e^((1/5)ln(e^((2/(4!))ln((1/2))) )) =e^((2/(5!))ln((1/2)))       a_5 =((1/2))^(((1/3))^(((1/4))^(((1/5))^(((1/6))) ) ) ) =e^((1/6)ln(a_4 )) =e^((1/6)ln(e^((2/(5!))ln((1/2))) )) =e^((2/(6!))ln((1/2)))       ....       ...     a_n =((1/2))^(((1/3))^(.....((1/(n+1)))) ) =e^((1/((n+1)))ln(a_(n−1) )) =e^((1/((n+1)))ln(e^((2/(n!))ln((1/2))) )) =e^((2/((n+1)!))ln((1/2)))   et  :n>0   (n+1)<(n+1)!<(n+1)^((n+1))    ⇒   n>0    (2/((n+1)))>(2/((n+1)!))>(2/((n+1)^((n+1)) ))        n>0       ((1/2))^(((2/(n+1)))) <((1/2))^(((2/((n+1)!)))) < ((1/2))^(2/((n+1)^((n+1)) ))   ⇒ n>0 .  ((1/2))^(((2/(n+1)))) <a_n =e^((2/((n+1)!))ln((1/2))) <((1/2))^(2/((n+1)^((n+1)) ))    donc   : lim_(n→∞) ((1/2))^(2/((n+1))) < lim_(n→∞) a_n <lim_(n→∞) ((1/2))^(2/((n+1)^((n+1)) )) ⇒   n>0    1<lim_(n→∞) a_n <1  en fin:( lim_(n→∞) a_n =1)

solution:onaan=(12)(13)(14)........(1n+1).a1=(12).a2=(12)(13)=e13ln12a3=(12)(13)(14)=e14ln((12)(13))=e14ln(a2)=e14ln(e13ln(12))=e24!ln(12)a4=(12)(13)(14)(15)=e15ln((12)(13)(14))=e15ln(a3)=e15ln(e24!ln(12))=e25!ln(12)a5=(12)(13)(14)(15)(16)=e16ln(a4)=e16ln(e25!ln(12))=e26!ln(12).......an=(12)(13).....(1n+1)=e1(n+1)ln(an1)=e1(n+1)ln(e2n!ln(12))=e2(n+1)!ln(12)et:n>0(n+1)<(n+1)!<(n+1)(n+1)n>02(n+1)>2(n+1)!>2(n+1)(n+1)n>0(12)(2n+1)<(12)(2(n+1)!)<(12)2(n+1)(n+1)n>0.(12)(2n+1)<an=e2(n+1)!ln(12)<(12)2(n+1)(n+1)Double subscripts: use braces to clarifyDouble subscripts: use braces to clarify

Commented by Dwaipayan Shikari last updated on 24/Jun/20

I  had  a  thought like you.Our thinking is matched. Great sir

Ihadathoughtlikeyou.Ourthinkingismatched.Greatsir

Commented by Dwaipayan Shikari last updated on 24/Jun/20

Just matched!!But i was not so sure about answer. Sir you create my belief

Justmatched!!Butiwasnotsosureaboutanswer.Siryoucreatemybelief

Commented by bachamohamed last updated on 24/Jun/20

 thank′s

thanks

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