So far I have referred to the gradient function in exercises. There are two representations that you will commonly see for this and in solving problems rather than being asked to find the gradient function you may instead be asked

• to find the derivative

or

• to differentiate a function

For example Differentiate In answer to this, you could write . Note that we read this as the derivative of y with respect to x. Although we will often use variables x and y we can use other variables as well, t is commonly used to represent time and we may say If then . In this case we would say that the derivative of s with respect to t is 2t. In other cases we use a dash to represent differentiation and or and