Given: A=43i−33j−5k^

As incident vector A makes i angle with normal Z-axis and refracted vector R makes r angle with normal Z- axis.
The angle made by the incident ray with the normal is given as
i=cos−1(AAz)=cos−1((43)2+(33)2+525)
=cos−1(105)⇒i=60∘
Applying Snell's law of refraction at the interface of two media
μ1sini=μ2sinr
⇒2sin60∘=3×sinr
⇒r=45∘
Difference between i and r =60∘−45∘=15∘