Do the Mach waves upstream of an oblique-shock wave intersect with the shock? Assuming supersonic downstream flow,

Question:

Do the Mach waves upstream of an oblique-shock wave intersect with the shock? Assuming supersonic downstream flow, do the downstream Mach waves intersect the shock? Show that for small deflections the shock-wave angle β lies halfway between μ1 and μ2 + θ for any Mach number.