Phase plane
(重定向自Phase plane method)

![Classification of equilibrium points of a linear autonomous system.[1] These profiles also arise for non-linear autonomous systems in linearized approximations.](/uploads/202502/02/Phase_plane_nodes.svg4136.png)
In applied mathematics, in particular the context of nonlinear system analysis, a phase plane is a visual display of certain characteristics of certain kinds of differential equations; a coordinate plane with axes being the values of the two state variables, say (x, y), or (q, p) etc. (any pair of variables). It is a two-dimensional case of the general n-dimensional phase space.