Solution (source code)

= Solution

Tangential velocity is unchanged, while the downstream normal velocity is $Uρ_1/ρ_2$. Thus the incident and outgoing angles to the shock have tangents $1$ and $ρ_1/ρ_2$. Using the tangent-difference identity, the ratio from part (b), and $M^2=2U^2/c_1^2$ gives
$$
\boxed{\tanδ={M^2-2\over γM^2+2}.}
$$