###

## SAGE (or MAPLE)

SAGE is a free open-source mathematics software system which combines
the power of many existing open-source packages into a common
Python-based interface.

You can download this software or use it online at the following address
www.sagemath.org/
To try sage online you can do so by following the appropriate links at
the above address and selecting one of the OpenID providers (say, for example,
Google or Yahoo).
SAGE is easy to use to plot direction (slope) fields of a differential equation
using the command *plot_slope_field*. For example,
the snapshot below shows the SAGE commands to plot the direction (slope)
field of the differential equation
*dy/dx = *sin*(x)**sin*(y)*

Alternatively, if you have access to the software *MAPLE*, the
direction (slope) fields of a some autonomous differential equations
(and the relative commands that produce them) can be found
here.