# calculating a limit of sequence

Can some one help to show that for $a>0$

My tries : I was not able to use riemann sum for calculating.
For the special case $a=1$ the RHS has limit $1$ and for the LHS for $a=1$ we can write

so the limit of LHS is $1$ . For arbitrary $a$ I have failed to answer.

The left- and right-most sides of $(*)$ converge to