So far I have referred to the [b]gradient function[/b] 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[br][list][*][i][b]to find the derivative[/b][/i][/*][/list][br]or[br][list][*][i][b]to differentiate a function[br][/b][/i][/*][/list][br]For example [br][br]Differentiate [math]y=x^2+3[/math][br][br]In answer to this, you could write [math]\frac{dy}{dx}=2x[/math]. Note that we read this as [b]the derivative of [i]y[/i] with respect to [/b][i][b]x[/b]. [br][br][/i]Although we will often use variables [i]x[/i] and [i]y[/i] we can use other variables as well, t is commonly used to represent time and we may say[br][br]If [math]s=t^2+3[/math] then [math]\frac{ds}{dt}=2t[/math]. [br][br]In this case we would say that the derivative [b]of [/b][i]s [/i][b]with respect to [/b][i]t[/i] is 2t.[br][br]In other cases we use a dash to represent differentiation[br][br][math]y=x^2+3[/math] and [math]y'=2x[/math][br][br]or[br][br][math]f\left(x\right)=x^2+3[/math] and [math]f'\left(x\right)=2x[/math]