Definition:Mutually Consistent Boundary Conditions

Definition
Let $\map {\mathbf y} x$, $\map {\boldsymbol\psi} {\mathbf y}$ be an N-dimensional vectors.

Consider the differential equations:


 * $\mathbf y''=\map {\mathbf f} {x,\mathbf y,\mathbf y'}\paren{\star}$

Let derivatives of $\mathbf y$ satisfy:


 * $\mathbf y'\vert_{x=x_1}=\map{\boldsymbol\psi^{\paren 1} } {\mathbf y}\vert_{x=x_1}$


 * $\mathbf y'\vert_{x=x_2}=\map{\boldsymbol\psi^{\paren 2} } {\mathbf y}\vert_{x=x_2}$

If every solution of $\paren{\star}$ satisfying conditions at $x=x_1$ automatically satisfies conditions at $x=x_2$ (or vice versa), then these boundary conditions are called mutually consistent.