How do you find a rate of change, in any context, and express it mathematically? You use differentiation. Tutorials in differentiating logs and exponentials, sines and cosines, and 3 key rules explained, providing excellent reference material for undergraduate study.
Maxima and minima
Because the derivative provides information about the gradient of a graph of a function, we can use it to locate points on a graph where the gradient is zero. Such points are often associated with the largest or smallest values of the function, at least in their immediate locality. Video tutorial 38 mins.