\(\vec{v}_{r / m}=\vec{v}_{r}-\vec{v}_{m}\)

\(\tan 60^{\circ}=\frac{ V _{ r }}{ v _{ m }}=\sqrt{3}\)

\(v _{ r }= v _{ m } \sqrt{3}= v \sqrt{3}\)

Now, \(v _{ m }=(1+ B ) v\)

and \(\theta=45^{\circ}\)

\(\tan 45=\frac{ v _{ r }}{ v _{ m }}=1\)

\(v _{ r }= v _{ m }\)

\(v \sqrt{3}=(1+\beta) v\)

\(\sqrt{3}=1+\beta\)

\(\Rightarrow \beta=\sqrt{3}-1=0.73\)