Sometimes, we are interested in the minima or maxima of a function, rather than the zero crossings. For example, an engineer might define a function that estimates the cost of a product. Finding the minimum of this function will help the engineer design a product with the lowest cost. Conversely, one might want to maximize a function that represents the performance of a system. The problem of finding minima and maxima is a form of numerical optimization, which we'll cover later in the chapter.