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The program can display **functions** and parametric **curves** in
the construction, or use **user defined functions** of one or more
parameters in other expressions. It is also possible to display the
zero set of a function of two variables.

First, we describe the type of functions for display in the construction window. In the dialog, enter the start and stop value of the parameter variable and the step size. If you wish, you can use any string not containing blanks as a parameter name. The default is "x".

For a function, leave the X-value empty or set it to "x", and enter an expression dependong on "x" for the Y-value. For a parametric curve, one needs two expressions, one for the X-value and one for the Y-value.

The program will increment the parameter variable from start to end using the given step size. If the function is valid between two parameter steps, a line segment is drawn in the construction using the construction coordinates.

This type of functions can be used in other functions. The Y-value will be evaluated then.

Functions and curves can be filled. For a parametric curve, the center is
0, but can be changed. To do that use the **properties** dialog and
press the "Select Center" button. Functions can be reduced to a
sequence of points. If a function is filled additionally, a Riemann
step function will be drawn.

Display functions or curves can intersect with other objects, and points can be fixed on the function graph. Geometrically these functions behave like a curve.

User defined functions of several variables cannot be plotted. Their
purpose is to be used in other expressions. Consequently, there is a
much simpler dialog for these functions, which can be called by
holding the **ctrl-key** while pressing the function icon. One has to
declare all variables, separated by blanks, in this dialog. The
variables may then be used in the expression. There is only one
expression, of course. The function will display its definition,
unless it is hidden, of course. The display can be moved as usual.

The program can plot and display the **zero sets** of user defined
functions in two dimensions. There is a switch in the settings dialog
to show this set. Use any two variables and an expression in these
variables.

Related topics: Syntax for Expressions, Object Properties

Next topic: Default settings