In general, a system of ordinary differential equations (ODEs) can be expressed in the normal form, The derivatives of the dependent variables x are expressed explicitly in terms of the independent transient variable t and the dependent variables x. As long as the function f has sufficient continuity, a unique solution can always be found for an initial value problem where the values of the dependent variables are given at a specific value of the independent variable. With differential-algebraic equations (DAEs), the derivatives are not, in general, expressed explicitly. In fact, derivatives of some of the dependent variables typically do not appear in the equations. For example, the following equation