1/ln(n+2)+1/ln(n+3)+...+1/ln(2n+1)>1/2,n是自然数证明题

Question

1/ln(n+2)+1/ln(n+3)+...+1/ln(2n+1)>1/2,n是自然数 证明题

Answer 1

首先证明n>1时lnn1)
y'=(1/x)-11/(n+1)+1/(n+2)+.1/2n
>1/2n+1/2n+.1/2n=1/2