ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)怎么化简

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/26 16:22:01
ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)怎么化简ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)怎么化简ln(1+1)+ln(1

ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)怎么化简
ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)怎么化简

ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)怎么化简
利用对数的运算法则
lgM+lgN=lg(MN)
ln(1+1)+ln(1+1/2)+ln(1+1/3)+…ln(1+1/n-1)
=ln2+ln(3/2)+ln(4/3)+.+ln[n/(n-1)]
=ln[2*(3/2)*(4/3)*.*n/(n-1)]
=ln n
(ps:你这样写,应该有条件n≥1)

=ln(2/1)+ln(3/2)+ln(4/3)+....+ln[n/(n-1)]
=(ln2-ln1)+(ln3-ln2)+(ln4-ln3)+...+[lnn-ln(n-1)]
=lnn-ln1
=lnn

因为ln(1+1/n)=ln[(1+n)/n]=ln(1+n)-ln n
∴ ln(1+1)+ln(1+1/2)=ln(1+1)-ln1+ln(1+2)-ln2=ln(1+2)
∴原式=ln(1+(n-1))=ln(n) n大于等于2

ln(1+1/(n-1))=ln[(n-1+1)/(n-1)]=ln[n/(n-1)]=ln(n)-ln(n-1)
原式化为
ln2-ln1+ln3-ln2+ln4-ln3……=-ln1+ln(n)=ln(n)