Some commands change the internal state of the calculation, so the results have to be different each time. For example, if x is 1, entering x:=x+1; repeatedly obviously yields values of x that count up. A less obvious way that a command can do different things different times it is used is if it includes the % reference to the previous result. Then, the result from the command will depend on what the previous result was. It is less confusing to assign a name to a result you want to use again, rather than referring to it with %.

To undefine x, enter x:='x'; To restart Maple with its memory cleared, enter restart.

Help with using the simple Maple Commands

Any questions that apply to plotting in Maple will appear here.

A1: You forgot to specify a range on the independent variable.

 > f:=2-x;
 > plot(f);              WRONG
 Plotting error, empty plot
 > plot(f,x=-1..1);      RIGHT
 

A2: You might be plotting a quantity that isn't defined. For example, you might have defined Y but then asked Maple to plot y. Maple is case-sensitive, and many strange behaviors are the result of typing a variable name in the wrong case.

Another way a plotted quantity can be undefined is if you didn't use the assignment operator := to define it.

 > y=sin(x);              WRONG