\(\Rightarrow \quad \sin \theta=\frac{1}{\mu}\)

\({\mu \sin \theta=1.5 \sin r}\)

\({\mu \tan \theta=1.5}\)

\( \Rightarrow \tan \theta  = \frac{{1.5}}{\mu }\)

\(\sin \theta  = \frac{3}{{\sqrt {9 + 4{\mu ^2}} }} = \frac{1}{\mu }\)

\(9{\mu ^2} = 9 + 4{\mu ^2}\)

\( \Rightarrow \mu  = \frac{3}{{\sqrt 5 }}\)