# Derivative test

## Method for finding the extrema of a function / From Wikipedia, the free encyclopedia

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In calculus, a **derivative test** uses the derivatives of a function to locate the critical points of a function and determine whether each point is a local maximum, a local minimum, or a saddle point. Derivative tests can also give information about the concavity of a function.

The usefulness of derivatives to find extrema is proved mathematically by Fermat's theorem of stationary points.