Now it's time for you to practice writing a command in Mathematica.
However, first you must `open' a line to type in as follows:
1. Move the cursor slowly down between two paragraphs (e.g. between
this paragraph and the next one) until the cursor becomes a horizontal
I-beam.
2. Click the mouse; a grey line will appear across the window.
For practice, after opening a line, type the same Mathematica command that we worked with above, and execute the command. (Remember: to execute a command, first `select' it by clicking behind the command, and then hit the Enter key.)