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.
Differentiation from first principles
What is differentiation? It is about rates of change - for example, the slope of a line is the rate of change of y with respect to x. To find the rate of change of a more general function, it is necessary to take a limit. This is done explicitly for a simple quadratic function. Video tutorial 30 mins.