Ex8 2

$\def\abs#1{|#1|}\def\i{\mathbf {i}}\def\ket#1{|{#1}\rangle}\def\bra#1{\langle{#1}|}\def\braket#1#2{\langle{#1}|{#2}\rangle}\def\tr{\mathord{\mbox{tr}}}\mathbf{Exercise\ 8.2}$

Show that with high probability $v$, the value obtained from the quantum core of Shor's alorithm described in section 8.2.1 is within $\frac{1}{2}$ of some multiple of $\frac{2^n}{r}$,