ESDU AERO S.00.03.23 gives curves of shock angle plotted against flow deflection angle for various values of the density ratio across the shock. When the shock angle is known the deflection is determined directly and conditions in the equilibrium zone behind the shock are obtained using the equations of ESDU AERO S.00.03.22 with upstream Mach number being taken as the component normal to the shock. In the more usual case when the flow deflection is known, a range of shock angles is selected increasing from either the Mach angle or the flow deflection angle, whichever is the greater. For each angle the ratio of the densities across the shock is obtained from ESDU S.00.03.22 as before. Values of flow deflection appropriate to each shock angle are then read from the curves and by cross plotting the shock angle at the given initial conditions is found. The conditions behind the shock then follow.