If there is a

function *f* on an interval

*I* which contains the point

*c,* *c* is a critical point if at least one of the following is true:

1. *c* is an end point on the interval *I*.

2. *c* is a stationary point(Where the slope of the tangent(derivative) is equal to 0).

3. *c* is a singular point(Where the derivative does not exist).

Critical points can help you find out where the function is increasing and/or decreasing which in turn can help you find minima and maxima.