Stationary Points

In calculus, a stationary point of a differentiable function describes a point on the function’s graph where the derivative is zero. It can be thought of as the point at which the function stops changing, neither increasing nor decreasing. If a differentiable function consists of several variables, the stationary point describes a point on the graph’s surface where all of its partial derivatives are zero. Visualizing a stationary point on the graph of one variable is not difficult, as it is the point on the graph where the tangent is horizontal. But for a graph of two variables, the stationary point would have a tangent plane parallel to the xy-plane.