"Descartes allows you to easily draw graphs of mathematical functions."

"This is the command window where you can give values to the variables, calculate expressions, define and evaluate functions and so on."

"Implicitly-defined functions can be plotted. Here we are looking at a quadratic curve"

"Parametrically-defined curves can be drawn, using any variable as the parameter."

"A built-in function which performs numerical differentiation is also available."

"This shows the chord feature. A chord is displayed together with the slope value."

"Functions can be plotted using polar co-ordinates, with any variable representing the angle."

"Inequalities can be shown. This is the region defined by sin(x) >0 and y > x"

"This picture shows the basic idea - easily plotting 3 functions."