Autodesk 057B1-41A111-1001 - AutoCAD LT 2010, Руководство пользователя

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The Length and Width dimensional constraint parameters are set to constants.
The d1 and d2 constraints are simple expressions that reference the Length
and Width. The Radius dimensional constraint parameter is set to an expression
that includes the square root function, parentheses to determine the
precedence of operations, the Area user variable, the division operator, and
the constant, PI.
As you can see, part of the equation for determining the area of the circle is
included in the Radius dimensional constraint parameter and part was defined
as a user variable. Alternatively, the entire expression, sqrt (Length * Width /
PI), could have been assigned to the Radius dimensional constraint parameter,
defined in a user variable, or some other combination.
Protect Expressions in Dynamic Constraints
When a dynamic dimensional constraint references one or more parameters, the
prefix fx: is added to the name of the constraint. This prefix is displayed only
in the drawing. Its purpose is to help you avoid accidentally overwriting
parameters and formulas when the dimension name format is set to Value or
Name, which suppresses the display of the parameters and formulas.
Control Geometry with Parameters
You can create and manage custom parameters that can be used with
dimensional constraints (dynamic and annotational).
The -PARAMETERS command allows you to do the following operations:
■ Edit the expression of a parameter
■ Rename a parameter
■ Delete a parameter from the drawing
264 | Chapter 6 Create and Modify Objects