Solution of Biquadratic Equations

IN applications of mathematics to aerodynamics, the biquadratic or quartic equation is of frequentoccurrence.Itarises forinstance in studies of aircraft stability as the characteristic equation which determines the frequencies and dampings of the lateral, or, alternatively, the longitudinal modes of motion of an aircraft with fixed controls, following a disturbance from steady flight; and in other cases, as, for example, in the study of the stability of an aircraft with free controls or of a towed glider, it may occur in the course of the solution of an equation of higher order.