15-20 Equation Writer
NOTE
This operation supposes that the current variable is also 
the variable of the function or curve you want to graph. 
When the expression is copied, it is evaluated, and the 
current variable (contained in VX) is changed to X, T, or 
θ, depending on the type of plot you chose. 
If the function depends on a parameter, it is preferable to 
give the parameter a value before pressing  . If, 
however, you want the parameterized expression to be 
copied with its parameter, then the name of the 
parameter must consist of a single letter other than X, T, 
or θ, so that there is no confusion. If the highlighted 
expression has real values, the Function, Aplet or Polar 
Aplet can be chosen, and the graph will be of Function or 
Polar type. If the highlighted expression has complex 
values, the Parametric Aplet must be chosen, and the 
graph will be of Parametric type. 
To summarize. If you choose:
• the Function Aplet, the highlighted expression is 
copied into the chosen function Fi, and the current 
variable is changed to X.
• the Parametric Aplet, the real part and the imaginary 
part of the highlighted expression are copied into the 
chosen functions Xi,Yi, and the current variable is 
changed to T.
• the Polar Aplet, the highlighted expression is copied 
into the chosen function Ri and the current variable is 
changed to θ.
NUM key  Pressing   in the Equation Writer causes the 
highlighted expression to be replaced by a numeric 
approximation.   puts the calculator into 
approximate mode.
SHIFT NUM key  Pressing   in the Equation Writer causes the 
highlighted expression to be replaced by a rational 
number.   puts the calculator into exact 
mode.
VIEWS key  Pressing   in the Equation Writer enables you to 
move the cursor with the   and   arrow keys to see 
the entire highlighted expression. Press   to return in 
the Equation Writer. 
hp40g+.book  Page 20  Friday, December 9, 2005  12:27 AM