Question: A thin flat plate is placed in a uniform air flow in which the Mach number is 2.3 and the pressure is 10 kPa. The plate is set at an angle to the flow, and as a result, an oblique shock wave originating at the leading edge of the lower surface of the plate is generated, and an expansion wave originating at the leading edge of the upper surface of the plate is generated. The oblique shock wave makes an angle of 40° to the direction of the undisturbed flow upstream of the plate. Find the angle at which the plate is set relative to the undisturbed flow direction and the pressures acting on the upper and lower surfaces of the plate.